
BASH(1)                                                                BASH(1)



NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989-2005 by the Free Software Foundation, Inc.

DESCRIPTION
       Bash  is  an  sh-compatible  command language interpreter that executes
       commands read from the standard input or from a file.  Bash also incor-
       porates useful features from the Korn and _C shells (ksh and csh).

       Bash  is  intended  to be a conformant implementation of the IEEE POSIX
       Shell and Tools specification (IEEE Working Group 1003.2).  Bash can be
       configured to be POSIX-conformant by default.

OPTIONS
       In  addition  to  the  single-character shell options documented in the
       description of the set builtin command, bash interprets  the  following
       options when it is invoked:

       -c string If  the  -c  option  is  present, then commands are read from
                 string.  If there are arguments after the  string,  they  are
                 assigned to the positional parameters, starting with $$00.
       -i        If the -i option is present, the shell is interactive.
       -l        Make bash act as if it had been invoked as a login shell (see
                 INVOCATION below).
       -r        If the -r option is present,  the  shell  becomes  restricted
                 (see RESTRICTED SHELL below).
       -s        If  the -s option is present, or if no arguments remain after
                 option processing, then commands are read from  the  standard
                 input.   This  option  allows the positional parameters to be
                 set when invoking an interactive shell.
       -D        A list of all double-quoted strings preceded by $$ is  printed
                 on  the standard output.  These are the strings that are sub-
                 ject to language translation when the current locale is not CC
                 or  POSIX.   This  implies the -n option; no commands will be
                 executed.
       [-+]O [[shopt__option]]
                 shopt__option is one of the  shell  options  accepted  by  the
                 shopt   builtin  (see  SHELL  BUILTIN  COMMANDS  below).   If
                 shopt__option is present, -O sets the value of that option; +O
                 unsets  it.   If  shopt__option is not supplied, the names and
                 values of the shell options accepted by shopt are printed  on
                 the  standard  output.   If  the invocation option is ++OO, the
                 output is displayed in a format that may be reused as  input.
       ----        A  ----  signals the end of options and disables further option
                 processing.  Any arguments after the ---- are treated as  file-
                 names and arguments.  An argument of -- is equivalent to ----.

       Bash  also  interprets  a  number  of  multi-character  options.  These
       options must appear on the command  line  before  the  single-character
       options to be recognized.

       --debugger
              Arrange for the debugger profile to be executed before the shell
              starts.  Turns on extended debugging mode (see  the  description
              of  the  extdebug  option  to the shopt builtin below) and shell
              function tracing (see the description of the -o functrace option
              to the set builtin below).
       --dump-po-strings
              Equivalent  to -D, but the output is in the GNU gettext po (por-
              table object) file format.
       --dump-strings
              Equivalent to -D.
       --help Display a usage message on standard  output  and  exit  success-
              fully.
       --init-file file
       --rcfile file
              Execute commands from file instead of the standard personal ini-
              tialization file ~/.bashrc if  the  shell  is  interactive  (see
              INVOCATION below).

       --login
              Equivalent to -l.

       --noediting
              Do  not  use the GNU readline library to read command lines when
              the shell is interactive.

       --noprofile
              Do not read either the system-wide startup file /etc/profile  or
              any   of  the  personal  initialization  files  ~/.bash__profile,
              ~/.bash__login, or ~/.profile.   By  default,  bash  reads  these
              files  when  it  is  invoked  as  a  login shell (see INVOCATION
              below).

       --norc Do  not  read  and  execute  the  personal  initialization  file
              ~/.bashrc  if  the  shell  is interactive.  This option is on by
              default if the shell is invoked as sh.

       --posix
              Change the behavior of bash where the default operation  differs
              from  the  POSIX  1003.2  standard  to match the standard (posix
              mode).

       --restricted
              The shell becomes restricted (see RESTRICTED SHELL below).

       --verbose
              Equivalent to  -v.

       --version
              Show version information for this instance of bash on the  stan-
              dard output and exit successfully.

ARGUMENTS
       If arguments remain after option processing, and neither the -c nor the
       -s option has been supplied, the first argument is assumed  to  be  the
       name  of  a file containing shell commands.  If bash is invoked in this
       fashion, $$00 is set to the name of the file, and the positional  parame-
       ters  are set to the remaining arguments.  Bash reads and executes com-
       mands from this file, then exits.  Bash's exit status is the exit  sta-
       tus  of  the  last  command executed in the script.  If no commands are
       executed, the exit status is 0.  An attempt is first made to  open  the
       file in the current directory, and, if no file is found, then the shell
       searches the directories in PATH for the script.

INVOCATION
       A login shell is one whose first character of argument zero is a --,  or
       one started with the --login option.

       An  interactive  shell  is one started without non-option arguments and
       without the -c option whose standard input and error are both connected
       to  terminals  (as determined by isatty(3)), or one started with the -i
       option.  PS1 is set and $$-- includes ii if bash is interactive,  allowing
       a shell script or a startup file to test this state.

       The  following paragraphs describe how bash executes its startup files.
       If any of the files exist but cannot be read, bash  reports  an  error.
       Tildes are expanded in file names as described below under Tilde Expan-
       sion in the EXPANSION section.

       When bash is invoked as an interactive login shell, or as a  non-inter-
       active  shell with the --login option, it first reads and executes com-
       mands from the file /etc/profile, if that file exists.   After  reading
       that file, it looks for ~/.bash__profile, ~/.bash__login, and ~/.profile,
       in that order, and reads and executes commands from the first one  that
       exists  and  is  readable.  The --noprofile option may be used when the
       shell is started to inhibit this behavior.

       When a login shell exits, bash reads and  executes  commands  from  the
       file ~/.bash__logout, if it exists.

       When  an  interactive  shell that is not a login shell is started, bash
       reads and executes commands from ~/.bashrc, if that file exists.   This
       may  be inhibited by using the --norc option.  The --rcfile file option
       will force bash to read and  execute  commands  from  file  instead  of
       ~/.bashrc.

       When  bash  is  started  non-interactively,  to run a shell script, for
       example, it looks for the variable BASH_ENV in the environment, expands
       its  value if it appears there, and uses the expanded value as the name
       of a file to read and execute.  Bash behaves as if the  following  com-
       mand were executed:
              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but  the  value of the PATH variable is not used to search for the file
       name.

       If bash is invoked with the name sh, it  tries  to  mimic  the  startup
       behavior  of  historical  versions  of sh as closely as possible, while
       conforming to the POSIX standard as well.  When invoked as an  interac-
       tive  login  shell, or a non-interactive shell with the --login option,
       it first attempts to read and execute commands  from  /etc/profile  and
       ~/.profile,  in  that  order.   The  --noprofile  option may be used to
       inhibit this behavior.  When invoked as an interactive shell  with  the
       name  sh,  bash  looks for the variable ENV, expands its value if it is
       defined, and uses the expanded value as the name of a file to read  and
       execute.  Since a shell invoked as sh does not attempt to read and exe-
       cute commands from any other startup files, the --rcfile option has  no
       effect.   A  non-interactive  shell  invoked  with the name sh does not
       attempt to read any other startup files.   When  invoked  as  sh,  bash
       enters posix mode after the startup files are read.

       When  bash  is  started in posix mode, as with the --posix command line
       option, it follows the POSIX standard for startup files.  In this mode,
       interactive  shells  expand  the ENV variable and commands are read and
       executed from the file whose name is  the  expanded  value.   No  other
       startup files are read.

       Bash  attempts  to  determine  when it is being run by the remote shell
       daemon, usually rshd.  If bash determines it is being run by  rshd,  it
       reads  and executes commands from ~/.bashrc, if that file exists and is
       readable.  It will not do this if invoked as sh.  The --norc option may
       be  used  to inhibit this behavior, and the --rcfile option may be used
       to force another file to be read, but rshd does  not  generally  invoke
       the shell with those options or allow them to be specified.

       If the shell is started with the effective user (group) id not equal to
       the real user (group) id, and the -p option is not supplied, no startup
       files are read, shell functions are not inherited from the environment,
       the SHELLOPTS variable, if it appears in the environment,  is  ignored,
       and the effective user id is set to the real user id.  If the -p option
       is supplied at invocation, the startup behavior is the  same,  but  the
       effective user id is not reset.

DEFINITIONS
       The  following  definitions  are used throughout the rest of this docu-
       ment.
       blank  A space or tab.
       word   A sequence of characters considered as  a  single  unit  by  the
              shell.  Also known as a token.
       name   A  word  consisting  only  of alphanumeric characters and under-
              scores, and beginning with an alphabetic character or an  under-
              score.  Also referred to as an identifier.
       metacharacter
              A  character  that,  when unquoted, separates words.  One of the
              following:
              ||  && ;; (( )) << >> space tab
       control operator
              A token that performs a control function.  It is one of the fol-
              lowing symbols:
              |||| && &&&& ;; ;;;; (( )) || <newline>

RESERVED WORDS
       Reserved words are words that have a special meaning to the shell.  The
       following words are recognized as reserved when unquoted and either the
       first  word  of a simple command (see SHELL GRAMMAR below) or the third
       word of a case or for command:

       !! case  do done elif else esac fi for function if in select then  until
       while {{ }} time [[[[ ]]]]

SHELL GRAMMAR
   Simple Commands
       A  simple  command  is a sequence of optional variable assignments fol-
       lowed by blank-separated words and redirections, and  terminated  by  a
       control operator.  The first word specifies the command to be executed,
       and is passed as argument zero.  The  remaining  words  are  passed  as
       arguments to the invoked command.

       The  return  value  of a simple command is its exit status, or 128+_n if
       the command is terminated by signal _n.

   Pipelines
       A pipeline is a sequence of one or more commands separated by the char-
       acter ||.  The format for a pipeline is:

              [time [-p] [ ! ] command [ || command2 ... ]

       The  standard output of command is connected via a pipe to the standard
       input of command2.  This connection is performed  before  any  redirec-
       tions specified by the command (see REDIRECTION below).

       The return status of a pipeline is the exit status of the last command,
       unless the pipefail option is enabled.  If  pipefail  is  enabled,  the
       pipeline's  return  status is the value of the last (rightmost) command
       to exit with a non-zero status, or zero if all commands  exit  success-
       fully.  If the reserved word !!  precedes a pipeline, the exit status of
       that pipeline is the logical negation of the exit status  as  described
       above.   The  shell waits for all commands in the pipeline to terminate
       before returning a value.

       If the time reserved word precedes a pipeline, the elapsed as  well  as
       user  and  system  time consumed by its execution are reported when the
       pipeline terminates.  The -p option changes the output format  to  that
       specified  by  POSIX.   The  TIMEFORMAT variable may be set to a format
       string that specifies how the timing information should  be  displayed;
       see the description of TIMEFORMAT under Shell Variables below.

       Each  command in a pipeline is executed as a separate process (i.e., in
       a subshell).

   Lists
       A list is a sequence of one or more pipelines separated by one  of  the
       operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or
       <newline>.

       Of these list operators, &&&& and |||| have equal precedence, followed by ;;
       and &&,, which have equal precedence.

       A  sequence  of  one or more newlines may appear in a list instead of a
       semicolon to delimit commands.

       If a command is terminated by the control operator &&,  the  shell  exe-
       cutes  the command in the background in a subshell.  The shell does not
       wait for the command to finish, and the return status is  0.   Commands
       separated  by  a  ;; are executed sequentially; the shell waits for each
       command to terminate in turn.  The return status is the exit status  of
       the last command executed.

       The  control operators &&&& and |||| denote AND lists and OR lists, respec-
       tively.  An AND list has the form

              command1 &&&& command2

       command2 is executed if, and only if, command1 returns an  exit  status
       of zero.

       An OR list has the form

              command1 |||| command2


       command2  is  executed  if and only if command1 returns a non-zero exit
       status.  The return status of AND and OR lists is the  exit  status  of
       the last command executed in the list.

   Compound Commands
       A compound command is one of the following:

       (list) list  is  executed in a subshell environment (see COMMAND EXECU-
              TION ENVIRONMENT below).  Variable assignments and builtin  com-
              mands  that  affect  the  shell's  environment  do not remain in
              effect after the command completes.  The return  status  is  the
              exit status of list.

       { list; }
              list  is simply executed in the current shell environment.  list
              must be terminated with a newline or semicolon.  This  is  known
              as  a  group  command.   The return status is the exit status of
              list.  Note that unlike the metacharacters (( and )), {{ and }}  are
              reserved words and must occur where a reserved word is permitted
              to be recognized.  Since they do not cause a  word  break,  they
              must be separated from list by whitespace.

       ((expression))
              The  expression  is  evaluated  according to the rules described
              below under ARITHMETIC EVALUATION.  If the value of the  expres-
              sion  is  non-zero, the return status is 0; otherwise the return
              status is 1.  This is exactly equivalent to let ""expression"".

       [[[[ expression ]]]]
              Return a status of 0 or 1 depending on  the  evaluation  of  the
              conditional  expression expression.  Expressions are composed of
              the primaries described  below  under  CONDITIONAL  EXPRESSIONS.
              Word  splitting  and pathname expansion are not performed on the
              words between the [[[[ and  ]]]];  tilde  expansion,  parameter  and
              variable  expansion, arithmetic expansion, command substitution,
              process substitution, and quote removal are  performed.   Condi-
              tional operators such as -f must be unquoted to be recognized as
              primaries.

              When the ==== and !!== operators are used, the string to  the  right
              of the operator is considered a pattern and matched according to
              the rules described below under Pattern Matching.  If the  shell
              option  nocasematch  is  enabled, the match is performed without
              regard to the case of alphabetic characters.  The  return  value
              is  0  if  the  string  matches  or  does not match the pattern,
              respectively, and 1 otherwise.  Any part of the pattern  may  be
              quoted to force it to be matched as a string.

              An  additional  binary operator, ==~~, is available, with the same
              precedence as ==== and !!==.  When it is used,  the  string  to  the
              right  of the operator is considered an extended regular expres-
              sion and matched accordingly (as in regex(3)).  The return value
              is 0 if the string matches the pattern, and 1 otherwise.  If the
              regular expression is syntactically incorrect,  the  conditional
              expression's return value is 2.  If the shell option nocasematch
              is enabled, the match is performed without regard to the case of
              alphabetic  characters.   Substrings  matched  by  parenthesized
              subexpressions within the regular expression are  saved  in  the
              array  variable  BASH_REMATCH.  The element of BASH_REMATCH with
              index 0 is the portion of the string matching the entire regular
              expression.   The  element  of  BASH_REMATCH with index _n is the
              portion of the string matching the _nth parenthesized  subexpres-
              sion.

              Expressions  may  be  combined  using  the  following operators,
              listed in decreasing order of precedence:

              (( expression ))
                     Returns the value of expression.  This  may  be  used  to
                     override the normal precedence of operators.
              !! expression
                     True if expression is false.
              expression1 &&&& expression2
                     True if both expression1 and expression2 are true.
              expression1 |||| expression2
                     True if either expression1 or expression2 is true.

              The &&&& and |||| operators do not evaluate expression2 if the value
              of expression1 is sufficient to determine the  return  value  of
              the entire conditional expression.

       for name [ in word ] ; do list ; done
              The list of words following in is expanded, generating a list of
              items.  The variable name is set to each element of this list in
              turn,  and  list is executed each time.  If the in word is omit-
              ted, the for command executes  list  once  for  each  positional
              parameter that is set (see PARAMETERS below).  The return status
              is the exit status of the last command that  executes.   If  the
              expansion of the items following in results in an empty list, no
              commands are executed, and the return status is 0.

       for (( expr1 ; expr2 ; expr3 )) ; do list ; done
              First, the arithmetic expression expr1 is evaluated according to
              the  rules  described  below  under  ARITHMETIC EVALUATION.  The
              arithmetic expression expr2 is then evaluated  repeatedly  until
              it  evaluates  to zero.  Each time expr2 evaluates to a non-zero
              value, list is executed and the arithmetic expression  expr3  is
              evaluated.   If  any  expression is omitted, it behaves as if it
              evaluates to 1.  The return value is the exit status of the last
              command in list that is executed, or false if any of the expres-
              sions is invalid.

       select name [ in word ] ; do list ; done
              The list of words following in is expanded, generating a list of
              items.   The  set  of  expanded words is printed on the standard
              error, each preceded by a number.  If the in  word  is  omitted,
              the  positional  parameters  are printed (see PARAMETERS below).
              The PS3 prompt is then displayed and a line read from the  stan-
              dard  input.   If the line consists of a number corresponding to
              one of the displayed words, then the value of  name  is  set  to
              that  word.  If the line is empty, the words and prompt are dis-
              played again.  If EOF is read, the command completes.  Any other
              value  read  causes  name  to  be set to null.  The line read is
              saved in the variable REPLY.  The list is  executed  after  each
              selection until a break command is executed.  The exit status of
              select is the exit status of the last command executed in  list,
              or zero if no commands were executed.

       case word in [ [(] pattern [ || pattern ] ... ) list ;; ] ... esac
              A case command first expands word, and tries to match it against
              each pattern in turn, using the same matching rules as for path-
              name  expansion  (see  Pathname  Expansion below).  If the shell
              option nocasematch is enabled, the match  is  performed  without
              regard  to  the  case of alphabetic characters.  When a match is
              found, the corresponding list  is  executed.   After  the  first
              match,  no subsequent matches are attempted.  The exit status is
              zero if no pattern matches.  Otherwise, it is the exit status of
              the last command executed in list.

       if list; then list; [ elif list; then list; ] ... [ else list; ] fi
              The  if  list is executed.  If its exit status is zero, the then
              list is executed.  Otherwise, each  elif  list  is  executed  in
              turn,  and  if  its  exit status is zero, the corresponding then
              list is executed and the command completes.  Otherwise, the else
              list  is executed, if present.  The exit status is the exit sta-
              tus of the last command executed, or zero if no condition tested
              true.

       while list; do list; done
       until list; do list; done
              The  while  command continuously executes the do list as long as
              the last command in list returns an exit status  of  zero.   The
              until command is identical to the while command, except that the
              test is negated; the do list is executed as  long  as  the  last
              command in list returns a non-zero exit status.  The exit status
              of the while and until commands is the exit status of  the  last
              do list command executed, or zero if none was executed.

   Shell Function Definitions
       A  shell function is an object that is called like a simple command and
       executes a compound command with a new set  of  positional  parameters.
       Shell functions are declared as follows:

       [ function ] name () compound-command [redirection]
              This  defines a function named name.  The reserved word function
              is optional.  If the function reserved  word  is  supplied,  the
              parentheses  are optional.  The body of the function is the com-
              pound command compound-command (see  Compound  Commands  above).
              That  command is usually a list of commands between { and }, but
              may be any command listed under Compound Commands  above.   com-
              pound-command is executed whenever name is specified as the name
              of a simple command.  Any redirections (see  REDIRECTION  below)
              specified  when  a  function  is  defined are performed when the
              function is executed.  The exit status of a function  definition
              is zero unless a syntax error occurs or a readonly function with
              the same name already exists.  When executed, the exit status of
              a  function  is  the exit status of the last command executed in
              the body.  (See FUNCTIONS below.)

COMMENTS
       In a non-interactive shell, or an interactive shell in which the inter-
       active_comments  option  to  the  shopt  builtin  is enabled (see SHELL
       BUILTIN COMMANDS below), a word beginning with ## causes that  word  and
       all  remaining  characters  on that line to be ignored.  An interactive
       shell without the interactive_comments option enabled  does  not  allow
       comments.  The interactive_comments option is on by default in interac-
       tive shells.

QUOTING
       Quoting is used to remove the special meaning of certain characters  or
       words  to  the shell.  Quoting can be used to disable special treatment
       for special characters, to prevent reserved words from being recognized
       as such, and to prevent parameter expansion.

       Each  of  the metacharacters listed above under DEFINITIONS has special
       meaning to the shell and must be quoted if it is to represent itself.

       When the command history expansion facilities are being used (see  HIS-
       TORY EXPANSION below), the history expansion character, usually !!, must
       be quoted to prevent history expansion.

       There are  three  quoting  mechanisms:  the  escape  character,  single
       quotes, and double quotes.

       A  non-quoted  backslash (\\) is the escape character.  It preserves the
       literal value of the next character that follows, with the exception of
       <newline>.   If  a  \\<newline>  pair  appears, and the backslash is not
       itself quoted, the \\<newline> is treated as a line  continuation  (that
       is, it is removed from the input stream and effectively ignored).

       Enclosing  characters  in  single quotes preserves the literal value of
       each character within the quotes.  A single quote may not occur between
       single quotes, even when preceded by a backslash.

       Enclosing  characters  in  double quotes preserves the literal value of
       all characters within the quotes, with the exception of $$, ``,  \\,  and,
       when  history  expansion  is enabled, !!.  The characters $$ and `` retain
       their special meaning within double quotes.  The backslash retains  its
       special  meaning only when followed by one of the following characters:
       $$, ``, "", \\, or <newline>.  A double quote may be quoted  within  double
       quotes by preceding it with a backslash.  If enabled, history expansion
       will be performed unless an !!  appearing in double  quotes  is  escaped
       using a backslash.  The backslash preceding the !!  is not removed.

       The  special  parameters  **  and  @@ have special meaning when in double
       quotes (see PARAMETERS below).

       Words of the form $$'string' are treated specially.  The word expands to
       string,  with backslash-escaped characters replaced as specified by the
       ANSI C standard.  Backslash escape sequences, if present,  are  decoded
       as follows:
              \a     alert (bell)
              \b     backspace
              \e     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\\\     backslash
              \\''     single quote
              \\nnn   the  eight-bit  character  whose value is the octal value
                     nnn (one to three digits)
              \\xx_H_H   the eight-bit character whose value  is  the  hexadecimal
                     value HH (one or two hex digits)
              \\cc_x    a control-_x character

       The  expanded  result  is  single-quoted, as if the dollar sign had not
       been present.

       A double-quoted string preceded by a dollar sign  ($$)  will  cause  the
       string  to  be translated according to the current locale.  If the cur-
       rent locale is CC or POSIX, the dollar sign is ignored.  If  the  string
       is translated and replaced, the replacement is double-quoted.

PARAMETERS
       A  parameter is an entity that stores values.  It can be a name, a num-
       ber, or one of the special characters listed below under Special Param-
       eters.   A variable is a parameter denoted by a name.  A variable has a
       value and zero or more attributes.  Attributes are assigned  using  the
       declare  builtin command (see declare below in SHELL BUILTIN COMMANDS).

       A parameter is set if it has been assigned a value.  The null string is
       a  valid  value.  Once a variable is set, it may be unset only by using
       the unset builtin command (see SHELL BUILTIN COMMANDS below).

       A variable may be assigned to by a statement of the form

              name=[value]

       If value is not given, the variable is assigned the null  string.   All
       values  undergo tilde expansion, parameter and variable expansion, com-
       mand substitution, arithmetic expansion, and quote removal (see  EXPAN-
       SION below).  If the variable has its integer attribute set, then value
       is evaluated as an arithmetic expression even if the $((...)) expansion
       is  not  used  (see Arithmetic Expansion below).  Word splitting is not
       performed, with the exception of ""$$@@"" as explained below under  Special
       Parameters.   Pathname  expansion  is not performed.  Assignment state-
       ments may also appear as arguments  to  the  alias,  declare,  typeset,
       export, readonly, and local builtin commands.

       In  the context where an assignment statement is assigning a value to a
       shell variable or array index, the += operator can be used to append to
       or add to the variable's previous value.  When += is applied to a vari-
       able for which the integer attribute has been set, value  is  evaluated
       as  an arithmetic expression and added to the variable's current value,
       which is also evaluated.  When += is applied to an array variable using
       compound  assignment  (see  Arrays  below), the variable's value is not
       unset (as it is when using =), and new values are appended to the array
       beginning  at one greater than the array's maximum index.  When applied
       to a string-valued variable, value is  expanded  and  appended  to  the
       variable's value.

   Positional Parameters
       A  positional  parameter  is a parameter denoted by one or more digits,
       other than the single digit 0.  Positional parameters are assigned from
       the  shell's  arguments when it is invoked, and may be reassigned using
       the set builtin command.  Positional parameters may not be assigned  to
       with  assignment statements.  The positional parameters are temporarily
       replaced when a shell function is executed (see FUNCTIONS below).

       When a positional parameter consisting of more than a single  digit  is
       expanded, it must be enclosed in braces (see EXPANSION below).

   Special Parameters
       The  shell  treats  several parameters specially.  These parameters may
       only be referenced; assignment to them is not allowed.
       **      Expands to the positional parameters, starting from  one.   When
              the  expansion occurs within double quotes, it expands to a sin-
              gle word with the value of each parameter separated by the first
              character of the IFS special variable.  That is, "$$**" is equiva-
              lent to "$$11_c$$22_c......", where _c is the first character of the value
              of  the IFS variable.  If IFS is unset, the parameters are sepa-
              rated by spaces.  If IFS is  null,  the  parameters  are  joined
              without intervening separators.
       @@      Expands  to  the positional parameters, starting from one.  When
              the  expansion  occurs  within  double  quotes,  each  parameter
              expands to a separate word.  That is, "$$@@" is equivalent to "$$11"
              "$$22" ...  If the double-quoted expansion occurs within  a  word,
              the  expansion  of the first parameter is joined with the begin-
              ning part of the original word, and the expansion  of  the  last
              parameter  is  joined  with  the last part of the original word.
              When there are no positional parameters, "$$@@" and $$@@  expand  to
              nothing (i.e., they are removed).
       ##      Expands to the number of positional parameters in decimal.
       ??      Expands  to  the status of the most recently executed foreground
              pipeline.
       --      Expands to the current option flags as  specified  upon  invoca-
              tion,  by  the  set  builtin  command, or those set by the shell
              itself (such as the -i option).
       $$      Expands to the process ID of the shell.  In a  ()  subshell,  it
              expands  to  the  process  ID of the current shell, not the sub-
              shell.
       !!      Expands to the process ID of the most  recently  executed  back-
              ground (asynchronous) command.
       00      Expands  to  the name of the shell or shell script.  This is set
              at shell initialization.  If bash is invoked with a file of com-
              mands,  $$00  is set to the name of that file.  If bash is started
              with the -c option, then $$00 is set to the first  argument  after
              the  string to be executed, if one is present.  Otherwise, it is
              set to the file name used to invoke bash, as given  by  argument
              zero.
       __      At  shell  startup,  set to the absolute pathname used to invoke
              the shell or shell script being executed as passed in the  envi-
              ronment  or  argument  list.   Subsequently, expands to the last
              argument to the previous command, after expansion.  Also set  to
              the  full  pathname  used  to  invoke  each command executed and
              placed in the environment exported to that command.  When check-
              ing  mail,  this  parameter holds the name of the mail file cur-
              rently being checked.

   Shell Variables
       The following variables are set by the shell:

       BASH   Expands to the full file name used to invoke  this  instance  of
              bash.
       BASH_ARGC
              An  array  variable whose values are the number of parameters in
              each frame of the current bash execution call stack.  The number
              of  parameters  to  the  current  subroutine  (shell function or
              script executed with .. or source) is at the top  of  the  stack.
              When  a  subroutine is executed, the number of parameters passed
              is pushed onto BASH_ARGC.  The shell sets BASH_ARGC only when in
              extended  debugging  mode  (see  the description of the extdebug
              option to the shopt builtin below)
       BASH_ARGV
              An array variable containing all of the parameters in  the  cur-
              rent bash execution call stack.  The final parameter of the last
              subroutine call is at the top of the stack; the first  parameter
              of the initial call is at the bottom.  When a subroutine is exe-
              cuted, the parameters supplied are pushed onto  BASH_ARGV.   The
              shell  sets  BASH_ARGV only when in extended debugging mode (see
              the description of the extdebug  option  to  the  shopt  builtin
              below)
       BASH_COMMAND
              The  command  currently  being executed or about to be executed,
              unless the shell is executing a command as the result of a trap,
              in  which  case  it  is the command executing at the time of the
              trap.
       BASH_EXECUTION_STRING
              The command argument to the -c invocation option.
       BASH_LINENO
              An array variable whose members are the line numbers  in  source
              files    corresponding    to    each    member    of   FUNCNAME.
              ${BASH_LINENO[_$_i]]}} is the line number in the source  file  where
              ${FUNCNAME[$ifP]]}}  was  called.   The  corresponding source file
              name is ${BASH_SOURCE[_$_i]]}}..  Use LINENO to  obtain  the  current
              line number.
       BASH_REMATCH
              An  array  variable  whose members are assigned by the ==~~ binary
              operator to the [[[[ conditional command.  The element with  index
              0  is  the  portion  of  the  string matching the entire regular
              expression.  The element with index _n  is  the  portion  of  the
              string matching the _nth parenthesized subexpression.  This vari-
              able is read-only.
       BASH_SOURCE
              An array variable whose members are the source filenames  corre-
              sponding to the elements in the FUNCNAME array variable.
       BASH_SUBSHELL
              Incremented  by one each time a subshell or subshell environment
              is spawned.  The initial value is 0.
       BASH_VERSINFO
              A readonly array variable whose members hold version information
              for  this  instance  of  bash.  The values assigned to the array
              members are as follows:
              BBAASSHH__VVEERRSSIINNFFOO[[0]]        The major version number (the  release).
              BBAASSHH__VVEERRSSIINNFFOO[[1]]        The  minor version number (the version).
              BBAASSHH__VVEERRSSIINNFFOO[[2]]        The patch level.
              BBAASSHH__VVEERRSSIINNFFOO[[3]]        The build version.
              BBAASSHH__VVEERRSSIINNFFOO[[4]]        The release status (e.g., beta1).
              BBAASSHH__VVEERRSSIINNFFOO[[5]]        The value of MACHTYPE.

       BASH_VERSION
              Expands to a string describing the version of this  instance  of
              bash.

       COMP_CWORD
              An  index  into ${COMP_WORDS} of the word containing the current
              cursor position.  This variable is available only in shell func-
              tions  invoked  by  the  programmable completion facilities (see
              Programmable Completion below).

       COMP_LINE
              The current command line.  This variable is  available  only  in
              shell  functions  and  external  commands  invoked  by  the pro-
              grammable completion  facilities  (see  Programmable  Completion
              below).

       COMP_POINT
              The  index of the current cursor position relative to the begin-
              ning of the current command.  If the current cursor position  is
              at the end of the current command, the value of this variable is
              equal to ${#COMP_LINE}.  This  variable  is  available  only  in
              shell  functions  and  external  commands  invoked  by  the pro-
              grammable completion  facilities  (see  Programmable  Completion
              below).

       COMP_WORDBREAKS
              The  set  of characters that the Readline library treats as word
              separators when performing word completion.  If  COMP_WORDBREAKS
              is  unset, it loses its special properties, even if it is subse-
              quently reset.

       COMP_WORDS
              An array variable (see Arrays below) consisting of the  individ-
              ual  words in the current command line.  This variable is avail-
              able only in shell functions invoked by the programmable comple-
              tion facilities (see Programmable Completion below).

       DIRSTACK
              An array variable (see Arrays below) containing the current con-
              tents of the directory stack.  Directories appear in  the  stack
              in  the order they are displayed by the dirs builtin.  Assigning
              to members of this array variable may be used to modify directo-
              ries  already in the stack, but the pushd and popd builtins must
              be used to add and remove directories.  Assignment to this vari-
              able  will  not  change  the  current directory.  If DIRSTACK is
              unset, it loses its special properties, even  if  it  is  subse-
              quently reset.

       EUID   Expands  to  the effective user ID of the current user, initial-
              ized at shell startup.  This variable is readonly.

       FUNCNAME
              An array variable containing the names of  all  shell  functions
              currently in the execution call stack.  The element with index 0
              is the name of any currently-executing shell function.  The bot-
              tom-most  element  is  "main".  This variable exists only when a
              shell function is executing.  Assignments to  FUNCNAME  have  no
              effect  and  return  an  error status.  If FUNCNAME is unset, it
              loses its special properties, even if it is subsequently  reset.

       GROUPS An  array  variable  containing  the list of groups of which the
              current user is a member.  Assignments to GROUPS have no  effect
              and  return  an  error status.  If GROUPS is unset, it loses its
              special properties, even if it is subsequently reset.

       HISTCMD
              The history number, or index in the history list, of the current
              command.   If HISTCMD is unset, it loses its special properties,
              even if it is subsequently reset.

       HOSTNAME
              Automatically set to the name of the current host.

       HOSTTYPE
              Automatically set to a string that uniquely describes  the  type
              of  machine  on which bash is executing.  The default is system-
              dependent.

       LINENO Each time this parameter is referenced, the shell substitutes  a
              decimal  number  representing the current sequential line number
              (starting with 1) within a script or function.  When  not  in  a
              script  or  function, the value substituted is not guaranteed to
              be meaningful.  If LINENO is unset, it loses its special proper-
              ties, even if it is subsequently reset.

       MACHTYPE
              Automatically  set  to  a string that fully describes the system
              type on which bash is executing, in the  standard  GNU  cpu-com-
              pany-system format.  The default is system-dependent.

       OLDPWD The previous working directory as set by the cd command.

       OPTARG The  value  of the last option argument processed by the getopts
              builtin command (see SHELL BUILTIN COMMANDS below).

       OPTIND The index of the next argument to be processed  by  the  getopts
              builtin command (see SHELL BUILTIN COMMANDS below).

       OSTYPE Automatically  set to a string that describes the operating sys-
              tem on which bash is executing.  The  default  is  system-depen-
              dent.

       PIPESTATUS
              An  array  variable (see Arrays below) containing a list of exit
              status values from the processes in  the  most-recently-executed
              foreground pipeline (which may contain only a single command).

       PPID   The  process  ID  of the shell's parent.  This variable is read-
              only.

       PWD    The current working directory as set by the cd command.

       RANDOM Each time this parameter is referenced, a random integer between
              0 and 32767 is generated.  The sequence of random numbers may be
              initialized by assigning a value to RANDOM.  If RANDOM is unset,
              it  loses  its  special  properties,  even if it is subsequently
              reset.

       REPLY  Set to the line of input read by the read builtin  command  when
              no arguments are supplied.

       SECONDS
              Each  time  this  parameter is referenced, the number of seconds
              since shell invocation is returned.  If a value is  assigned  to
              SECONDS,  the  value  returned upon subsequent references is the
              number of seconds since the assignment plus the value  assigned.
              If SECONDS is unset, it loses its special properties, even if it
              is subsequently reset.

       SHELLOPTS
              A colon-separated list of enabled shell options.  Each  word  in
              the  list  is  a  valid  argument  for  the -o option to the set
              builtin command (see SHELL BUILTIN COMMANDS below).  The options
              appearing  in  SHELLOPTS are those reported as on by set -o.  If
              this variable is in the environment when bash  starts  up,  each
              shell  option  in  the  list  will be enabled before reading any
              startup files.  This variable is read-only.

       SHLVL  Incremented by one each time an instance of bash is started.

       UID    Expands to the user ID of the current user, initialized at shell
              startup.  This variable is readonly.

       The  following  variables  are  used by the shell.  In some cases, bash
       assigns a default value to a variable; these cases are noted below.

       BASH_ENV
              If this parameter is set when bash is executing a shell  script,
              its  value  is  interpreted as a filename containing commands to
              initialize the shell, as in ~/.bashrc.  The value of BASH_ENV is
              subjected  to  parameter  expansion,  command  substitution, and
              arithmetic expansion before being interpreted as  a  file  name.
              PATH is not used to search for the resultant file name.
       CDPATH The  search  path for the cd command.  This is a colon-separated
              list of directories in which the  shell  looks  for  destination
              directories  specified  by  the  cd  command.  A sample value is
              ".:~:/usr".
       COLUMNS
              Used by the select builtin command  to  determine  the  terminal
              width  when  printing  selection  lists.  Automatically set upon
              receipt of a SIGWINCH.
       COMPREPLY
              An array variable from which bash reads the possible completions
              generated  by  a shell function invoked by the programmable com-
              pletion facility (see Programmable Completion below).
       EMACS  If bash finds this variable in the environment  when  the  shell
              starts  with  value "t", it assumes that the shell is running in
              an emacs shell buffer and disables line editing.
       FCEDIT The default editor for the fc builtin command.
       FIGNORE
              A colon-separated list of suffixes  to  ignore  when  performing
              filename completion (see READLINE below).  A filename whose suf-
              fix matches one of the entries in FIGNORE is excluded  from  the
              list of matched filenames.  A sample value is ".o:~".
       GLOBIGNORE
              A colon-separated list of patterns defining the set of filenames
              to be ignored by pathname expansion.  If a filename matched by a
              pathname  expansion  pattern also matches one of the patterns in
              GLOBIGNORE, it is removed from the list of matches.
       HISTCONTROL
              A colon-separated list of values controlling  how  commands  are
              saved  on  the  history  list.   If  the list of values includes
              ignorespace, lines which begin with a space  character  are  not
              saved  in  the history list.  A value of ignoredups causes lines
              matching the previous history entry to not be saved.  A value of
              ignoreboth is shorthand for ignorespace and ignoredups.  A value
              of erasedups causes all previous lines matching the current line
              to  be  removed from the history list before that line is saved.
              Any value not in the above list is ignored.  If  HISTCONTROL  is
              unset,  or does not include a valid value, all lines read by the
              shell parser are saved on the history list, subject to the value
              of  HISTIGNORE.  The second and subsequent lines of a multi-line
              compound command are not tested, and are added  to  the  history
              regardless of the value of HISTCONTROL.
       HISTFILE
              The name of the file in which command history is saved (see HIS-
              TORY below).  The default value is ~/.bash__history.   If  unset,
              the  command  history  is  not  saved  when an interactive shell
              exits.
       HISTFILESIZE
              The maximum number of lines contained in the history file.  When
              this  variable  is  assigned  a value, the history file is trun-
              cated, if necessary, to contain no  more  than  that  number  of
              lines.   The  default  value  is  500.  The history file is also
              truncated to this size after  writing  it  when  an  interactive
              shell exits.
       HISTIGNORE
              A  colon-separated list of patterns used to decide which command
              lines should be saved on the  history  list.   Each  pattern  is
              anchored  at  the  beginning of the line and must match the com-
              plete line (no implicit  `**'  is  appended).   Each  pattern  is
              tested  against  the line after the checks specified by HISTCON-
              TROL are applied.  In  addition  to  the  normal  shell  pattern
              matching characters, `&&' matches the previous history line.  `&&'
              may be escaped using  a  backslash;  the  backslash  is  removed
              before attempting a match.  The second and subsequent lines of a
              multi-line compound command are not tested, and are added to the
              history regardless of the value of HISTIGNORE.
       HISTSIZE
              The  number  of commands to remember in the command history (see
              HISTORY below).  The default value is 500.
       HISTTIMEFORMAT
              If this variable is set and not null, its value  is  used  as  a
              format string for strftime(3) to print the time stamp associated
              with each history entry displayed by the  history  builtin.   If
              this  variable  is  set,  time stamps are written to the history
              file so they may be preserved across shell sessions.
       HOME   The home directory of the current user; the default argument for
              the cd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HOSTFILE
              Contains the name of a file in the  same  format  as  /etc/hosts
              that should be read when the shell needs to complete a hostname.
              The list of possible hostname completions may be  changed  while
              the  shell  is  running;  the  next  time hostname completion is
              attempted after the value is changed, bash adds the contents  of
              the  new file to the existing list.  If HOSTFILE is set, but has
              no value, bash attempts to read /etc/hosts to obtain the list of
              possible  hostname  completions.   When  HOSTFILE  is unset, the
              hostname list is cleared.
       IFS    The Internal Field Separator that is  used  for  word  splitting
              after  expansion  and  to  split  lines into words with the read
              builtin  command.   The  default  value  is  ``<space><tab><new-
              line>''.
       IGNOREEOF
              Controls the action of an interactive shell on receipt of an EOF
              character as the sole input.  If set, the value is the number of
              consecutive  EOF  characters  which  must  be typed as the first
              characters on an input line before bash exits.  If the  variable
              exists  but  does not have a numeric value, or has no value, the
              default value is 10.  If it does not exist,  EOF  signifies  the
              end of input to the shell.
       INPUTRC
              The  filename  for  the  readline  startup  file, overriding the
              default of ~/.inputrc (see READLINE below).
       LANG   Used to determine the  locale  category  for  any  category  not
              specifically selected with a variable starting with LC_.
       LC_ALL This  variable  overrides  the  value  of LANG and any other LC_
              variable specifying a locale category.
       LC_COLLATE
              This variable determines the collation order used  when  sorting
              the  results  of pathname expansion, and determines the behavior
              of  range  expressions,  equivalence  classes,   and   collating
              sequences within pathname expansion and pattern matching.
       LC_CTYPE
              This  variable  determines  the interpretation of characters and
              the behavior of character classes within pathname expansion  and
              pattern matching.
       LC_MESSAGES
              This  variable  determines  the locale used to translate double-
              quoted strings preceded by a $$.
       LC_NUMERIC
              This variable determines the locale  category  used  for  number
              formatting.
       LINES  Used  by  the  select  builtin  command  to determine the column
              length for printing selection  lists.   Automatically  set  upon
              receipt of a SIGWINCH.
       MAIL   If  this  parameter is set to a file name and the MAILPATH vari-
              able is not set, bash informs the user of the arrival of mail in
              the specified file.
       MAILCHECK
              Specifies  how  often  (in  seconds)  bash checks for mail.  The
              default is 60 seconds.  When it is time to check for  mail,  the
              shell  does  so  before  displaying the primary prompt.  If this
              variable is unset, or set to  a  value  that  is  not  a  number
              greater than or equal to zero, the shell disables mail checking.
       MAILPATH
              A colon-separated list of file names to  be  checked  for  mail.
              The message to be printed when mail arrives in a particular file
              may be specified by separating the file name  from  the  message
              with a `?'.  When used in the text of the message, $$__ expands to
              the name of the current mailfile.  Example:
              MAILPATH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
              mail!"'
              Bash  supplies  a default value for this variable, but the loca-
              tion of the user mail files that it  uses  is  system  dependent
              (e.g., /var/mail/$USER).
       OPTERR If set to the value 1, bash displays error messages generated by
              the getopts builtin command (see SHELL BUILTIN COMMANDS  below).
              OPTERR  is  initialized to 1 each time the shell is invoked or a
              shell script is executed.
       PATH   The search path for commands.  It is a colon-separated  list  of
              directories  in  which the shell looks for commands (see COMMAND
              EXECUTION below).  A zero-length (null) directory  name  in  the
              value of PATH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bash.  A common  value  is
              ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
       POSIXLY_CORRECT
              If  this  variable  is  in the environment when bash starts, the
              shell enters posix mode before reading the startup files, as  if
              the  --posix  invocation option had been supplied.  If it is set
              while the shell is running, bash enables posix mode, as  if  the
              command set -o posix had been executed.
       PROMPT_COMMAND
              If set, the value is executed as a command prior to issuing each
              primary prompt.
       PS1    The value of this parameter is expanded  (see  PROMPTING  below)
              and  used  as  the  primary prompt string.  The default value is
              `\s-\v\$ ''.
       PS2    The value of this parameter is expanded as with PS1 and used  as
              the secondary prompt string.  The default is ``>> ''.
       PS3    The value of this parameter is used as the prompt for the select
              command (see SHELL GRAMMAR above).
       PS4    The value of this parameter is expanded  as  with  PS1  and  the
              value  is  printed  before  each command bash displays during an
              execution trace.  The first character of PS4 is replicated  mul-
              tiple  times, as necessary, to indicate multiple levels of indi-
              rection.  The default is ``++ ''.
       SHELL  The full pathname to the shell is kept in this environment vari-
              able.   If  it is not set when the shell starts, bash assigns to
              it the full pathname of the current user's login shell.
       TIMEFORMAT
              The value of this parameter is used as a format string  specify-
              ing  how  the timing information for pipelines prefixed with the
              time reserved word should be displayed.  The %% character  intro-
              duces  an  escape  sequence  that is expanded to a time value or
              other information.  The escape sequences and their meanings  are
              as follows; the braces denote optional portions.
              %%%%        A literal %%.
              %%[[_p]][[ll]]RR  The elapsed time in seconds.
              %%[[_p]][[ll]]UU  The number of CPU seconds spent in user mode.
              %%[[_p]][[ll]]SS  The number of CPU seconds spent in system mode.
              %P        The CPU percentage, computed as (%U + %S) / %R.

              The  optional  _p is a digit specifying the precision, the number
              of fractional digits after a decimal point.  A value of 0 causes
              no decimal point or fraction to be output.  At most three places
              after the decimal point may be specified; values  of  _p  greater
              than  3 are changed to 3.  If _p is not specified, the value 3 is
              used.

              The optional ll specifies a longer format, including minutes,  of
              the  form  _M_Mm_S_S._F_Fs.   The value of _p determines whether or not
              the fraction is included.

              If this variable is not set, bash acts as if it  had  the  value
              $'\nreal\t%3lR\nuser\t%3lU\nsys%3lS'.   If the value is null, no
              timing information is displayed.  A trailing  newline  is  added
              when the format string is displayed.

       TMOUT  If  set  to  a  value greater than zero, TMOUT is treated as the
              default timeout for the read builtin.  The select command termi-
              nates if input does not arrive after TMOUT seconds when input is
              coming from a terminal.  In an interactive shell, the  value  is
              interpreted  as  the  number  of seconds to wait for input after
              issuing the primary prompt.  Bash terminates after  waiting  for
              that number of seconds if input does not arrive.

       TMPDIR If  set, Bash uses its value as the name of a directory in which
              Bash creates temporary files for the shell's use.

       auto_resume
              This variable controls how the shell interacts with the user and
              job  control.   If this variable is set, single word simple com-
              mands without redirections are treated as candidates for resump-
              tion of an existing stopped job.  There is no ambiguity allowed;
              if there is more than one job beginning with the  string  typed,
              the  job  most  recently  accessed  is  selected.  The name of a
              stopped job, in this context, is the command line used to  start
              it.   If  set to the value exact, the string supplied must match
              the name of a stopped job exactly;  if  set  to  substring,  the
              string  supplied  needs  to  match  a substring of the name of a
              stopped job.  The substring value provides functionality  analo-
              gous  to the %%??  job identifier (see JOB CONTROL below).  If set
              to any other value, the supplied string must be a  prefix  of  a
              stopped job's name; this provides functionality analogous to the
              %%string job identifier.

       histchars
              The two or three characters which control history expansion  and
              tokenization (see HISTORY EXPANSION below).  The first character
              is the history expansion character, the character which  signals
              the  start  of  a  history  expansion, normally `!!'.  The second
              character is the quick substitution character, which is used  as
              shorthand  for  re-running the previous command entered, substi-
              tuting one string for another in the command.   The  default  is
              `^^'.   The optional third character is the character which indi-
              cates that the remainder of the line is a comment when found  as
              the  first  character of a word, normally `##'.  The history com-
              ment character causes history substitution to be skipped for the
              remaining  words on the line.  It does not necessarily cause the
              shell parser to treat the rest of the line as a comment.

   Arrays
       Bash provides one-dimensional array variables.   Any  variable  may  be
       used as an array; the declare builtin will explicitly declare an array.
       There is no maximum limit on the size of an array, nor any  requirement
       that  members  be indexed or assigned contiguously.  Arrays are indexed
       using integers and are zero-based.

       An array is created automatically if any variable is assigned to  using
       the  syntax  name[subscript]=value.   The  subscript  is  treated as an
       arithmetic expression that must evaluate to a number  greater  than  or
       equal  to  zero.   To  explicitly declare an array, use declare -a name
       (see SHELL BUILTIN COMMANDS below).  declare -a name[[subscript]] is also
       accepted; the subscript is ignored.  Attributes may be specified for an
       array variable using the declare and readonly builtins.  Each attribute
       applies to all members of an array.

       Arrays   are  assigned  to  using  compound  assignments  of  the  form
       name=((value_1 ... value_n)),  where  each  value  is  of  the  form  [sub-
       script]=string.  Only string is required.  If the optional brackets and
       subscript are supplied, that index is assigned to; otherwise the  index
       of  the element assigned is the last index assigned to by the statement
       plus one.  Indexing starts at zero.  This syntax is  also  accepted  by
       the  declare  builtin.   Individual  array  elements may be assigned to
       using the name[subscript]=value syntax introduced above.

       Any element of an array may  be  referenced  using  ${name[subscript]}.
       The braces are required to avoid conflicts with pathname expansion.  If
       subscript is @@ or **, the word expands to all members  of  name.   These
       subscripts  differ only when the word appears within double quotes.  If
       the word is double-quoted, ${name[*]} expands to a single word with the
       value  of each array member separated by the first character of the IFS
       special variable, and ${name[@]} expands each element of name to a sep-
       arate  word.   When  there  are no array members, ${name[@]} expands to
       nothing.  If the double-quoted expansion  occurs  within  a  word,  the
       expansion  of  the first parameter is joined with the beginning part of
       the original word, and the expansion of the last  parameter  is  joined
       with  the  last  part  of  the original word.  This is analogous to the
       expansion of the special parameters ** and  @@  (see  Special  Parameters
       above).   ${#name[subscript]}  expands  to  the  length  of ${name[sub-
       script]}.  If subscript is ** or @@, the expansion is the number of  ele-
       ments  in the array.  Referencing an array variable without a subscript
       is equivalent to referencing element zero.

       The unset builtin is used to  destroy  arrays.   unset  name[subscript]
       destroys  the  array element at index subscript.  Care must be taken to
       avoid unwanted side effects caused by filename generation.  unset name,
       where  name is an array, or unset name[subscript], where subscript is **
       or @@, removes the entire array.

       The declare, local, and readonly builtins each accept a  -a  option  to
       specify  an  array.   The  read builtin accepts a -a option to assign a
       list of words read from the standard input to an array.   The  set  and
       declare  builtins  display array values in a way that allows them to be
       reused as assignments.

EXPANSION
       Expansion is performed on the command line after it has been split into
       words.   There are seven kinds of expansion performed: brace expansion,
       tilde expansion, parameter and variable  expansion,  command  substitu-
       tion, arithmetic expansion, word splitting, and pathname expansion.

       The  order  of expansions is: brace expansion, tilde expansion, parame-
       ter, variable and arithmetic expansion and command  substitution  (done
       in a left-to-right fashion), word splitting, and pathname expansion.

       On systems that can support it, there is an additional expansion avail-
       able: process substitution.

       Only brace expansion, word splitting, and pathname expansion can change
       the  number of words of the expansion; other expansions expand a single
       word to a single word.  The only exceptions to this are the  expansions
       of "$$@@" and "$${{name[[@@]]}}" as explained above (see PARAMETERS).

   Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may be gener-
       ated.  This mechanism is similar to pathname expansion, but  the  file-
       names generated need not exist.  Patterns to be brace expanded take the
       form of an optional preamble, followed by either a series of comma-sep-
       arated  strings or a sequence expression between a pair of braces, fol-
       lowed by an optional postscript.  The  preamble  is  prefixed  to  each
       string contained within the braces, and the postscript is then appended
       to each resulting string, expanding left to right.

       Brace expansions may be nested.  The results of  each  expanded  string
       are  not  sorted;  left  to  right  order  is  preserved.  For example,
       a{{d,c,b}}e expands into `ade ace abe'.

       A sequence expression takes the form {{_x...._y}}, where _x and _y  are  either
       integers or single characters.  When integers are supplied, the expres-
       sion expands to each number between _x and _y, inclusive.   When  charac-
       ters  are  supplied,  the  expression expands to each character lexico-
       graphically between _x and _y, inclusive.  Note that both _x and _y must be
       of the same type.

       Brace expansion is performed before any other expansions, and any char-
       acters special to other expansions are preserved in the result.  It  is
       strictly  textual.  Bash does not apply any syntactic interpretation to
       the context of the expansion or the text between the braces.

       A correctly-formed brace expansion must contain  unquoted  opening  and
       closing  braces,  and  at  least one unquoted comma or a valid sequence
       expression.  Any incorrectly formed brace expansion is left  unchanged.
       A {{ or ,, may be quoted with a backslash to prevent its being considered
       part of a brace expression.  To avoid conflicts with  parameter  expan-
       sion, the string $${{ is not considered eligible for brace expansion.

       This construct is typically used as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace expansion introduces a  slight  incompatibility  with  historical
       versions  of sh.  sh does not treat opening or closing braces specially
       when they appear as part of a word, and preserves them in  the  output.
       Bash  removes  braces  from  words as a consequence of brace expansion.
       For example, a word entered to sh as file{1,2} appears  identically  in
       the  output.  The same word is output as file1 file2 after expansion by
       bash.  If strict compatibility with sh is desired, start bash with  the
       +B option or disable brace expansion with the +B option to the set com-
       mand (see SHELL BUILTIN COMMANDS below).

   Tilde Expansion
       If a word begins with an unquoted tilde character  (`~~'),  all  of  the
       characters  preceding  the  first unquoted slash (or all characters, if
       there is no unquoted slash) are considered a tilde-prefix.  If none  of
       the  characters  in  the tilde-prefix are quoted, the characters in the
       tilde-prefix following the tilde are treated as a possible login  name.
       If  this  login name is the null string, the tilde is replaced with the
       value of the shell parameter HOME.  If HOME is unset, the  home  direc-
       tory  of  the  user executing the shell is substituted instead.  Other-
       wise, the tilde-prefix is replaced with the home  directory  associated
       with the specified login name.

       If  the  tilde-prefix  is  a  `~+', the value of the shell variable PWD
       replaces the tilde-prefix.  If the tilde-prefix is a `~-', the value of
       the  shell variable OLDPWD, if it is set, is substituted.  If the char-
       acters following the tilde in the tilde-prefix consist of a  number  _N,
       optionally  prefixed  by  a  `+' or a `-', the tilde-prefix is replaced
       with the corresponding element from the directory stack, as it would be
       displayed by the dirs builtin invoked with the tilde-prefix as an argu-
       ment.  If the characters following the tilde in the  tilde-prefix  con-
       sist of a number without a leading `+' or `-', `+' is assumed.

       If the login name is invalid, or the tilde expansion fails, the word is
       unchanged.

       Each variable assignment is checked for unquoted tilde-prefixes immedi-
       ately following a :: or the first ==.  In these cases, tilde expansion is
       also performed.  Consequently, one may use file names  with  tildes  in
       assignments  to  PATH,  MAILPATH, and CDPATH, and the shell assigns the
       expanded value.

   Parameter Expansion
       The `$$' character introduces parameter expansion, command substitution,
       or  arithmetic  expansion.  The parameter name or symbol to be expanded
       may be enclosed in braces, which are optional but serve to protect  the
       variable  to be expanded from characters immediately following it which
       could be interpreted as part of the name.

       When braces are used, the matching ending brace is the  first  `}}'  not
       escaped  by  a  backslash  or within a quoted string, and not within an
       embedded  arithmetic  expansion,  command  substitution,  or  parameter
       expansion.

       ${parameter}
              The  value of parameter is substituted.  The braces are required
              when parameter is a positional  parameter  with  more  than  one
              digit, or when parameter is followed by a character which is not
              to be interpreted as part of its name.

       If the first character of parameter is an exclamation point, a level of
       variable  indirection  is introduced.  Bash uses the value of the vari-
       able formed from the rest of parameter as the  name  of  the  variable;
       this  variable  is  then expanded and that value is used in the rest of
       the substitution, rather than the value of parameter itself.   This  is
       known as indirect expansion.  The exceptions to this are the expansions
       of ${!prefix*} and ${!!name[_@]} described below.  The exclamation  point
       must  immediately  follow the left brace in order to introduce indirec-
       tion.

       In each of the cases below, word is subject to tilde expansion, parame-
       ter  expansion,  command  substitution, and arithmetic expansion.  When
       not performing substring expansion, bash tests for a parameter that  is
       unset  or null; omitting the colon results in a test only for a parame-
       ter that is unset.

       ${parameter::--word}
              Use Default Values.  If parameter is unset or null,  the  expan-
              sion  of word is substituted.  Otherwise, the value of parameter
              is substituted.
       ${parameter::==word}
              Assign Default Values.  If  parameter  is  unset  or  null,  the
              expansion of word is assigned to parameter.  The value of param-
              eter is then substituted.   Positional  parameters  and  special
              parameters may not be assigned to in this way.
       ${parameter::??word}
              Display  Error if Null or Unset.  If parameter is null or unset,
              the expansion of word (or a message to that effect  if  word  is
              not  present) is written to the standard error and the shell, if
              it is not interactive, exits.  Otherwise, the value of parameter
              is substituted.
       ${parameter::++word}
              Use  Alternate Value.  If parameter is null or unset, nothing is
              substituted, otherwise the expansion of word is substituted.
       ${parameter::offset}
       ${parameter::offset::length}
              Substring Expansion.  Expands to  up  to  length  characters  of
              parameter  starting  at  the  character specified by offset.  If
              length is omitted, expands to the substring of parameter  start-
              ing at the character specified by offset.  length and offset are
              arithmetic  expressions  (see  ARITHMETIC   EVALUATION   below).
              length  must evaluate to a number greater than or equal to zero.
              If offset evaluates to a number less than  zero,  the  value  is
              used  as  an  offset from the end of the value of parameter.  If
              parameter is @@,  the  result  is  length  positional  parameters
              beginning at offset.  If parameter is an array name indexed by @
              or *, the result is the length members of  the  array  beginning
              with  ${parameter[offset]}.  A negative offset is taken relative
              to one greater than the maximum index of  the  specified  array.
              Note  that a negative offset must be separated from the colon by
              at least one space to avoid being confused with  the  :-  expan-
              sion.   Substring  indexing  is zero-based unless the positional
              parameters are used, in which case the indexing starts at 1.

       ${!!prefix**}
       ${!!prefix@@}
              Expands to the names of variables whose names begin with prefix,
              separated by the first character of the IFS special variable.

       ${!!name[_@]}
       ${!!name[_*]}
              If  name  is  an  array  variable,  expands to the list of array
              indices (keys) assigned in name.   If  name  is  not  an  array,
              expands  to 0 if name is set and null otherwise.  When _@ is used
              and the expansion appears within double quotes, each key expands
              to a separate word.

       ${##parameter}
              The  length  in  characters of the value of parameter is substi-
              tuted.  If parameter is ** or @@, the  value  substituted  is  the
              number  of positional parameters.  If parameter is an array name
              subscripted by ** or @@, the value substituted is  the  number  of
              elements in the array.

       ${parameter##word}
       ${parameter####word}
              The  word  is  expanded to produce a pattern just as in pathname
              expansion.  If the pattern matches the beginning of the value of
              parameter,  then  the  result  of  the expansion is the expanded
              value of parameter with the shortest matching pattern (the ``##''
              case) or the longest matching pattern (the ``####'' case) deleted.
              If parameter is @@ or **, the pattern removal operation is applied
              to  each  positional parameter in turn, and the expansion is the
              resultant list.  If parameter is an array  variable  subscripted
              with  @@  or  **, the pattern removal operation is applied to each
              member of the array in turn, and the expansion is the  resultant
              list.

       ${parameter%%word}
       ${parameter%%%%word}
              The  word  is  expanded to produce a pattern just as in pathname
              expansion.  If the pattern matches a  trailing  portion  of  the
              expanded value of parameter, then the result of the expansion is
              the expanded value of parameter with the shortest matching  pat-
              tern  (the  ``%%''  case)  or  the  longest matching pattern (the
              ``%%%%'' case) deleted.  If parameter  is  @@  or  **,  the  pattern
              removal  operation  is  applied  to each positional parameter in
              turn, and the expansion is the resultant list.  If parameter  is
              an  array  variable subscripted with @@ or **, the pattern removal
              operation is applied to each member of the array  in  turn,  and
              the expansion is the resultant list.

       ${parameter//pattern//string}
       ${parameter////pattern//string}
              The pattern is expanded to produce a pattern just as in pathname
              expansion.  Parameter is expanded and the longest match of  pat-
              tern  against  its  value is replaced with string.  In the first
              form, only the first match is replaced.  The second form  causes
              all  matches  of pattern to be replaced with string.  If pattern
              begins with ##, it must match at the beginning  of  the  expanded
              value  of parameter.  If pattern begins with %%, it must match at
              the end of the expanded value of parameter.  If string is  null,
              matches  of  pattern are deleted and the // following pattern may
              be omitted.  If parameter is @@ or **, the substitution  operation
              is  applied to each positional parameter in turn, and the expan-
              sion is the resultant list.  If parameter is an  array  variable
              subscripted  with  @@ or **, the substitution operation is applied
              to each member of the array in turn, and the  expansion  is  the
              resultant list.

   Command Substitution
       Command substitution allows the output of a command to replace the com-
       mand name.  There are two forms:


              $$((command))
       or
              ``command``

       Bash performs the expansion by executing command and replacing the com-
       mand  substitution  with  the  standard output of the command, with any
       trailing newlines deleted.  Embedded newlines are not deleted, but they
       may  be  removed during word splitting.  The command substitution $(cat
       file)) can be replaced by the equivalent but faster $$((<< file)).

       When the old-style backquote form of substitution  is  used,  backslash
       retains  its  literal  meaning except when followed by $$, ``, or \\.  The
       first backquote not preceded by a backslash terminates the command sub-
       stitution.   When using the $(command) form, all characters between the
       parentheses make up the command; none are treated specially.

       Command substitutions may be nested.  To nest when using the backquoted
       form, escape the inner backquotes with backslashes.

       If  the  substitution  appears within double quotes, word splitting and
       pathname expansion are not performed on the results.

   Arithmetic Expansion
       Arithmetic expansion allows the evaluation of an arithmetic  expression
       and  the  substitution of the result.  The format for arithmetic expan-
       sion is:

              $$((((expression))))

       The expression is treated as if it were within  double  quotes,  but  a
       double  quote  inside  the  parentheses  is not treated specially.  All
       tokens in the expression undergo parameter expansion, string expansion,
       command  substitution, and quote removal.  Arithmetic expansions may be
       nested.

       The evaluation is performed according to the rules listed  below  under
       ARITHMETIC EVALUATION.  If expression is invalid, bash prints a message
       indicating failure and no substitution occurs.

   Process Substitution
       Process substitution is supported on systems that support  named  pipes
       (FIFOs)  or the /dev/fd method of naming open files.  It takes the form
       of <<((list)) or >>((list)).  The process list is run with its input or  out-
       put connected to a FIFO or some file in /dev/fd.  The name of this file
       is passed as an argument to the current command as the  result  of  the
       expansion.   If the >>((list)) form is used, writing to the file will pro-
       vide input for list.  If the <<((list)) form is used, the file  passed  as
       an argument should be read to obtain the output of list.

       When  available,  process substitution is performed simultaneously with
       parameter and variable expansion, command substitution, and  arithmetic
       expansion.

   Word Splitting
       The  shell  scans the results of parameter expansion, command substitu-
       tion, and arithmetic expansion that did not occur within double  quotes
       for word splitting.

       The  shell  treats each character of IFS as a delimiter, and splits the
       results of the other expansions into words on these characters.  If IFS
       is  unset,  or its value is exactly <space><tab><newline>, the default,
       then any sequence of IFS characters serves to delimit  words.   If  IFS
       has  a  value  other than the default, then sequences of the whitespace
       characters space and tab are ignored at the beginning and  end  of  the
       word,  as  long  as the whitespace character is in the value of IFS (an
       IFS whitespace character).  Any character in IFS that is not IFS white-
       space,  along  with  any adjacent IFS whitespace characters, delimits a
       field.  A sequence of IFS whitespace characters is also  treated  as  a
       delimiter.  If the value of IFS is null, no word splitting occurs.

       Explicit  null  arguments  (""""  or '''') are retained.  Unquoted implicit
       null arguments, resulting from the expansion of parameters that have no
       values,  are  removed.  If a parameter with no value is expanded within
       double quotes, a null argument results and is retained.

       Note that if no expansion occurs, no splitting is performed.

   Pathname Expansion
       After word splitting, unless the -f option has  been  set,  bash  scans
       each  word  for the characters **, ??, and [[.  If one of these characters
       appears, then the word is regarded as a pattern, and replaced  with  an
       alphabetically  sorted  list of file names matching the pattern.  If no
       matching file names are found, and the shell option  nullglob  is  dis-
       abled,  the word is left unchanged.  If the nullglob option is set, and
       no matches are found, the word  is  removed.   If  the  failglob  shell
       option  is  set,  and no matches are found, an error message is printed
       and the command is not executed.  If the  shell  option  nocaseglob  is
       enabled,  the  match  is performed without regard to the case of alpha-
       betic characters.  When a pattern is used for pathname  expansion,  the
       character  ````..''''   at  the  start  of a name or immediately following a
       slash must be matched explicitly, unless the shell  option  dotglob  is
       set.   When  matching  a  pathname,  the slash character must always be
       matched explicitly.  In  other  cases,  the  ````..''''   character  is  not
       treated  specially.   See  the  description  of shopt below under SHELL
       BUILTIN COMMANDS for a description of the nocaseglob,  nullglob,  fail-
       glob, and dotglob shell options.

       The  GLOBIGNORE  shell variable may be used to restrict the set of file
       names matching a pattern.  If GLOBIGNORE is  set,  each  matching  file
       name  that  also  matches  one of the patterns in GLOBIGNORE is removed
       from the list of matches.  The file names ````..''''  and ````....''''  are always
       ignored  when GLOBIGNORE is set and not null.  However, setting GLOBIG-
       NORE to a non-null value has the effect of enabling the  dotglob  shell
       option, so all other file names beginning with a ````..''''  will match.  To
       get the old behavior of ignoring file names  beginning  with  a  ````..'''',
       make  ````..**''''  one of the patterns in GLOBIGNORE.  The dotglob option is
       disabled when GLOBIGNORE is unset.

       Pattern Matching

       Any character that appears in a pattern, other than the special pattern
       characters  described below, matches itself.  The NUL character may not
       occur in a pattern.  A backslash escapes the following  character;  the
       escaping  backslash  is  discarded  when matching.  The special pattern
       characters must be quoted if they are to be matched literally.

       The special pattern characters have the following meanings:

       **      Matches any string, including the null string.
       ??      Matches any single character.
       [[......]]  Matches any one of the enclosed characters.  A pair  of  charac-
              ters separated by a hyphen denotes a range expression; any char-
              acter that sorts between those two characters, inclusive,  using
              the  current  locale's  collating sequence and character set, is
              matched.  If the first character following the [[ is a !!  or a  ^^
              then  any  character not enclosed is matched.  The sorting order
              of characters in range expressions is determined by the  current
              locale  and  the value of the LC_COLLATE shell variable, if set.
              A -- may be matched by including it as the first or last  charac-
              ter in the set.  A ]] may be matched by including it as the first
              character in the set.

              Within [[ and ]], character classes can  be  specified  using  the
              syntax  [[::class::]],  where  class is one of the following classes
              defined in the POSIX.2 standard:
              alnum alpha ascii blank cntrl  digit  graph  lower  print  punct
              space upper word xdigit
              A character class matches any character belonging to that class.
              The word character class matches letters, digits, and the  char-
              acter _.

              Within  [[ and ]], an equivalence class can be specified using the
              syntax [[==_c==]], which matches all characters with the same  colla-
              tion  weight (as defined by the current locale) as the character
              _c.

              Within [[ and ]], the syntax [[..symbol..]] matches the collating sym-
              bol symbol.

       If the extglob shell option is enabled using the shopt builtin, several
       extended pattern matching operators are recognized.  In  the  following
       description, a pattern-list is a list of one or more patterns separated
       by a ||.  Composite patterns may be formed using one or more of the fol-
       lowing sub-patterns:

              ??((pattern-list))
                     Matches zero or one occurrence of the given patterns
              **((pattern-list))
                     Matches zero or more occurrences of the given patterns
              ++((pattern-list))
                     Matches one or more occurrences of the given patterns
              @@((pattern-list))
                     Matches one of the given patterns
              !!((pattern-list))
                     Matches anything except one of the given patterns

   Quote Removal
       After the preceding expansions, all unquoted occurrences of the charac-
       ters \\, '', and "" that did not result from one of the  above  expansions
       are removed.

REDIRECTION
       Before  a  command  is executed, its input and output may be redirected
       using a special notation interpreted by  the  shell.   Redirection  may
       also  be  used  to open and close files for the current shell execution
       environment.  The following redirection operators may precede or appear
       anywhere within a simple command or may follow a command.  Redirections
       are processed in the order they appear, from left to right.

       In the following descriptions, if the file descriptor number  is  omit-
       ted,  and the first character of the redirection operator is <<, the re-
       direction refers to the standard input (file  descriptor  0).   If  the
       first  character  of  the  redirection  operator  is >>, the redirection
       refers to the standard output (file descriptor 1).

       The word following the redirection operator in the  following  descrip-
       tions,  unless  otherwise noted, is subjected to brace expansion, tilde
       expansion, parameter expansion, command substitution, arithmetic expan-
       sion,  quote  removal,  pathname  expansion, and word splitting.  If it
       expands to more than one word, bash reports an error.

       Note that the order of redirections is significant.  For  example,  the
       command

              ls >> dirlist 2>>&&1

       directs  both  standard  output and standard error to the file dirlist,
       while the command

              ls 2>>&&1 >> dirlist

       directs only the standard output to file dirlist, because the  standard
       error  was duplicated as standard output before the standard output was
       redirected to dirlist.

       Bash handles several filenames specially when they are used in redirec-
       tions, as described in the following table:

              /dev/fd/fd
                     If  fd  is  a valid integer, file descriptor fd is dupli-
                     cated.
              /dev/stdin
                     File descriptor 0 is duplicated.
              /dev/stdout
                     File descriptor 1 is duplicated.
              /dev/stderr
                     File descriptor 2 is duplicated.
              /dev/tcp/host//port
                     If host is a valid hostname or Internet address, and port
                     is  an integer port number or service name, bash attempts
                     to open a TCP connection to the corresponding socket.
              /dev/udp/host//port
                     If host is a valid hostname or Internet address, and port
                     is  an integer port number or service name, bash attempts
                     to open a UDP connection to the corresponding socket.

       A failure to open or create a file causes the redirection to fail.

       Redirections using file descriptors greater than 9 should be used  with
       care,  as they may conflict with file descriptors the shell uses inter-
       nally.

   Redirecting Input
       Redirection of input causes the file whose name results from the expan-
       sion  of  word  to  be  opened for reading on file descriptor _n, or the
       standard input (file descriptor 0) if _n is not specified.

       The general format for redirecting input is:

              [_n]<<word

   Redirecting Output
       Redirection of output causes the  file  whose  name  results  from  the
       expansion of word to be opened for writing on file descriptor _n, or the
       standard output (file descriptor 1) if _n is not specified.  If the file
       does  not exist it is created; if it does exist it is truncated to zero
       size.

       The general format for redirecting output is:

              [_n]>>word

       If the redirection operator is >>, and the noclobber option to  the  set
       builtin  has  been enabled, the redirection will fail if the file whose
       name results from the expansion of word exists and is a  regular  file.
       If the redirection operator is >>||, or the redirection operator is >> and
       the noclobber option to the set builtin command is not enabled, the re-
       direction is attempted even if the file named by word exists.

   Appending Redirected Output
       Redirection  of  output  in  this  fashion  causes  the file whose name
       results from the expansion of word to be opened for appending  on  file
       descriptor  _n,  or  the standard output (file descriptor 1) if _n is not
       specified.  If the file does not exist it is created.

       The general format for appending output is:

              [_n]>>>>word


   Redirecting Standard Output and Standard Error
       Bash allows both the standard output (file descriptor 1) and the  stan-
       dard  error  output  (file  descriptor  2) to be redirected to the file
       whose name is the expansion of word with this construct.

       There are two formats for  redirecting  standard  output  and  standard
       error:

              &&>>word
       and
              >>&&word

       Of the two forms, the first is preferred.  This is semantically equiva-
       lent to

              >>word 2>>&&1

   Here Documents
       This type of redirection instructs the shell to  read  input  from  the
       current  source  until  a  line  containing only word (with no trailing
       blanks) is seen.  All of the lines read up to that point are then  used
       as the standard input for a command.

       The format of here-documents is:

              <<<<[--]word
                      here-document
              delimiter

       No  parameter expansion, command substitution, arithmetic expansion, or
       pathname expansion is performed on word.  If any characters in word are
       quoted,  the  delimiter is the result of quote removal on word, and the
       lines in the here-document are not expanded.  If word is unquoted,  all
       lines  of  the here-document are subjected to parameter expansion, com-
       mand substitution, and arithmetic expansion.  In the latter  case,  the
       character  sequence  \<newline> is ignored, and \\ must be used to quote
       the characters \\, $$, and ``.

       If the redirection operator is <<<<--, then all leading tab characters are
       stripped  from  input  lines  and  the line containing delimiter.  This
       allows here-documents within shell scripts to be indented in a  natural
       fashion.

   Here Strings
       A variant of here documents, the format is:

              <<<<<<word

       The word is expanded and supplied to the command on its standard input.

   Duplicating File Descriptors
       The redirection operator

              [_n]<<&&word

       is used to duplicate input file descriptors.  If word expands to one or
       more  digits,  the file descriptor denoted by _n is made to be a copy of
       that file descriptor.  If the digits in word  do  not  specify  a  file
       descriptor  open for input, a redirection error occurs.  If word evalu-
       ates to --, file descriptor _n is closed.  If _n  is  not  specified,  the
       standard input (file descriptor 0) is used.

       The operator

              [_n]>>&&word

       is  used  similarly  to duplicate output file descriptors.  If _n is not
       specified, the standard output (file descriptor 1)  is  used.   If  the
       digits  in word do not specify a file descriptor open for output, a re-
       direction error occurs.  As a special case, if _n is omitted,  and  word
       does not expand to one or more digits, the standard output and standard
       error are redirected as described previously.

   Moving File Descriptors
       The redirection operator

              [_n]<<&&digit--

       moves the file descriptor digit to file descriptor _n, or  the  standard
       input (file descriptor 0) if _n is not specified.  digit is closed after
       being duplicated to _n.

       Similarly, the redirection operator

              [_n]>>&&digit--

       moves the file descriptor digit to file descriptor _n, or  the  standard
       output (file descriptor 1) if _n is not specified.

   Opening File Descriptors for Reading and Writing
       The redirection operator

              [_n]<<>>word

       causes  the  file  whose name is the expansion of word to be opened for
       both reading and writing on file descriptor _n, or on file descriptor  0
       if _n is not specified.  If the file does not exist, it is created.

ALIASES
       Aliases  allow a string to be substituted for a word when it is used as
       the first word of a simple command.  The  shell  maintains  a  list  of
       aliases  that  may  be set and unset with the alias and unalias builtin
       commands (see SHELL BUILTIN COMMANDS below).  The first  word  of  each
       simple  command, if unquoted, is checked to see if it has an alias.  If
       so, that word is replaced by the text of the alias.  The characters  //,
       $$,  ``,  and == and any of the shell metacharacters or quoting characters
       listed above may not appear in an alias name.  The replacement text may
       contain  any  valid  shell  input, including shell metacharacters.  The
       first word of the replacement text is tested for aliases,  but  a  word
       that  is  identical to an alias being expanded is not expanded a second
       time.  This means that one may alias ls to ls  -F,  for  instance,  and
       bash  does  not try to recursively expand the replacement text.  If the
       last character of the alias value is a blank,  then  the  next  command
       word following the alias is also checked for alias expansion.

       Aliases are created and listed with the alias command, and removed with
       the unalias command.

       There is no mechanism for using arguments in the replacement text.   If
       arguments  are  needed,  a shell function should be used (see FUNCTIONS
       below).

       Aliases are not expanded when the shell is not interactive, unless  the
       expand_aliases  shell option is set using shopt (see the description of
       shopt under SHELL BUILTIN COMMANDS below).

       The rules concerning the definition and use  of  aliases  are  somewhat
       confusing.   Bash  always  reads  at  least  one complete line of input
       before executing any  of  the  commands  on  that  line.   Aliases  are
       expanded  when  a command is read, not when it is executed.  Therefore,
       an alias definition appearing on the same line as another command  does
       not  take  effect  until  the next line of input is read.  The commands
       following the alias definition on that line are not affected by the new
       alias.   This  behavior  is  also an issue when functions are executed.
       Aliases are expanded when a function definition is read, not  when  the
       function  is  executed,  because a function definition is itself a com-
       pound command.  As a consequence, aliases defined in a function are not
       available  until  after  that function is executed.  To be safe, always
       put alias definitions on a separate line, and do not use alias in  com-
       pound commands.

       For almost every purpose, aliases are superseded by shell functions.

FUNCTIONS
       A  shell  function,  defined  as  described  above under SHELL GRAMMAR,
       stores a series of commands for later execution.  When the  name  of  a
       shell  function  is used as a simple command name, the list of commands
       associated with that function name is executed.  Functions are executed
       in  the  context  of  the  current  shell; no new process is created to
       interpret them (contrast this with the execution of  a  shell  script).
       When  a  function is executed, the arguments to the function become the
       positional parameters during its execution.  The special parameter ## is
       updated  to reflect the change.  Special parameter 0 is unchanged.  The
       first element of the FUNCNAME variable is set to the name of the  func-
       tion  while  the function is executing.  All other aspects of the shell
       execution environment are identical between a function and  its  caller
       with the exception that the DEBUG and RETURN traps (see the description
       of the trap builtin under SHELL BUILTIN COMMANDS below) are not  inher-
       ited  unless  the  function has been given the trace attribute (see the
       description of the declare builtin below) or  the  -o  functrace  shell
       option  has  been enabled with the set builtin (in which case all func-
       tions inherit the DEBUG and RETURN traps).

       Variables local to the function may be declared with the local  builtin
       command.  Ordinarily, variables and their values are shared between the
       function and its caller.

       If the builtin command return is executed in a function,  the  function
       completes  and  execution resumes with the next command after the func-
       tion call.  Any command associated with the  RETURN  trap  is  executed
       before execution resumes.  When a function completes, the values of the
       positional parameters and the special parameter ## are restored  to  the
       values they had prior to the function's execution.

       Function  names and definitions may be listed with the -f option to the
       declare or typeset builtin commands.  The -F option to declare or type-
       set  will  list the function names only (and optionally the source file
       and line number, if the extdebug shell option is  enabled).   Functions
       may  be exported so that subshells automatically have them defined with
       the -f option to the export builtin.  Note  that  shell  functions  and
       variables  with  the same name may result in multiple identically-named
       entries in the environment passed to the shell's children.  Care should
       be taken in cases where this may cause a problem.

       Functions  may  be  recursive.   No  limit  is imposed on the number of
       recursive calls.

ARITHMETIC EVALUATION
       The shell allows arithmetic expressions to be evaluated, under  certain
       circumstances  (see the let and declare builtin commands and Arithmetic
       Expansion).  Evaluation is done in fixed-width integers with  no  check
       for  overflow, though division by 0 is trapped and flagged as an error.
       The operators and their precedence, associativity, and values  are  the
       same  as in the C language.  The following list of operators is grouped
       into levels of equal-precedence operators.  The levels  are  listed  in
       order of decreasing precedence.

       id++++ id----
              variable post-increment and post-decrement
       ++++id ----id
              variable pre-increment and pre-decrement
       -- ++    unary minus and plus
       !! ~~    logical and bitwise negation
       ****     exponentiation
       ** // %%  multiplication, division, remainder
       ++ --    addition, subtraction
       <<<< >>>>  left and right bitwise shifts
       <<== >>== << >>
              comparison
       ==== !!==  equality and inequality
       &&      bitwise AND
       ^^      bitwise exclusive OR
       ||      bitwise OR
       &&&&     logical AND
       ||||     logical OR
       expr??expr::expr
              conditional operator
       == **== //== %%== ++== --== <<<<== >>>>== &&== ^^== ||==
              assignment
       expr1 ,, expr2
              comma

       Shell  variables  are  allowed as operands; parameter expansion is per-
       formed before the expression is evaluated.  Within an expression, shell
       variables  may  also  be referenced by name without using the parameter
       expansion syntax.  A shell variable that is null or unset evaluates  to
       0 when referenced by name without using the parameter expansion syntax.
       The value of a variable is evaluated as an arithmetic  expression  when
       it  is  referenced, or when a variable which has been given the integer
       attribute using declare -i is assigned a value.  A null value evaluates
       to  0.   A shell variable need not have its integer attribute turned on
       to be used in an expression.

       Constants with a leading 0 are interpreted as octal numbers.  A leading
       0x  or  0X  denotes  hexadecimal.   Otherwise,  numbers  take  the form
       [base#]n, where base is a decimal number between 2 and 64  representing
       the arithmetic base, and _n is a number in that base.  If base# is omit-
       ted, then base 10 is used.  The digits greater than 9  are  represented
       by  the  lowercase  letters,  the  uppercase letters, @, and _, in that
       order.  If base is less than or equal to 36,  lowercase  and  uppercase
       letters may be used interchangeably to represent numbers between 10 and
       35.

       Operators are evaluated in order  of  precedence.   Sub-expressions  in
       parentheses  are  evaluated first and may override the precedence rules
       above.

CONDITIONAL EXPRESSIONS
       Conditional expressions are used by the [[[[  compound  command  and  the
       test  and [[ builtin commands to test file attributes and perform string
       and arithmetic comparisons.  Expressions are formed from the  following
       unary  or  binary  primaries.   If any file argument to one of the pri-
       maries is of the form /dev/fd/n, then file descriptor _n is checked.  If
       the  file  argument  to  one  of  the  primaries  is one of /dev/stdin,
       /dev/stdout, or /dev/stderr, file descriptor 0, 1, or 2,  respectively,
       is checked.

       Unless otherwise specified, primaries that operate on files follow sym-
       bolic links and operate on the target of the link, rather than the link
       itself.

       -a file
              True if file exists.
       -b file
              True if file exists and is a block special file.
       -c file
              True if file exists and is a character special file.
       -d file
              True if file exists and is a directory.
       -e file
              True if file exists.
       -f file
              True if file exists and is a regular file.
       -g file
              True if file exists and is set-group-id.
       -h file
              True if file exists and is a symbolic link.
       -k file
              True if file exists and its ``sticky'' bit is set.
       -p file
              True if file exists and is a named pipe (FIFO).
       -r file
              True if file exists and is readable.
       -s file
              True if file exists and has a size greater than zero.
       -t fd  True if file descriptor fd is open and refers to a terminal.
       -u file
              True if file exists and its set-user-id bit is set.
       -w file
              True if file exists and is writable.
       -x file
              True if file exists and is executable.
       -O file
              True if file exists and is owned by the effective user id.
       -G file
              True if file exists and is owned by the effective group id.
       -L file
              True if file exists and is a symbolic link.
       -S file
              True if file exists and is a socket.
       -N file
              True  if  file  exists  and  has been modified since it was last
              read.
       file1 -nt file2
              True if file1 is newer (according  to  modification  date)  than
              file2, or if file1 exists and file2 does not.
       file1 -ot file2
              True  if file1 is older than file2, or if file2 exists and file1
              does not.
       file1 -ef file2
              True if file1 and file2 refer to the same device and inode  num-
              bers.
       -o optname
              True  if  shell  option  optname  is  enabled.   See the list of
              options under the description  of  the  -o  option  to  the  set
              builtin below.
       -z string
              True if the length of string is zero.
       string
       -n string
              True if the length of string is non-zero.

       string1 ==== string2
              True if the strings are equal.  == may be used in place of ==== for
              strict POSIX compliance.

       string1 !!== string2
              True if the strings are not equal.

       string1 << string2
              True if string1 sorts before string2  lexicographically  in  the
              current locale.

       string1 >> string2
              True  if  string1  sorts  after string2 lexicographically in the
              current locale.

       arg1 OP arg2
              OP is one of -eq, -ne, -lt, -le, -gt, or -ge.  These  arithmetic
              binary  operators return true if arg1 is equal to, not equal to,
              less than, less than or equal to, greater than, or greater  than
              or  equal  to arg2, respectively.  Arg1 and arg2 may be positive
              or negative integers.

SIMPLE COMMAND EXPANSION
       When a simple command is executed, the  shell  performs  the  following
       expansions, assignments, and redirections, from left to right.

       1.     The  words  that  the  parser has marked as variable assignments
              (those preceding the command name) and  redirections  are  saved
              for later processing.

       2.     The  words that are not variable assignments or redirections are
              expanded.  If any words remain after expansion, the  first  word
              is  taken  to be the name of the command and the remaining words
              are the arguments.

       3.     Redirections are performed as described above under REDIRECTION.

       4.     The text after the == in each variable assignment undergoes tilde
              expansion, parameter expansion, command substitution, arithmetic
              expansion,  and quote removal before being assigned to the vari-
              able.

       If no command name results, the variable assignments affect the current
       shell  environment.  Otherwise, the variables are added to the environ-
       ment of the executed command and do not affect the current shell  envi-
       ronment.   If  any  of  the assignments attempts to assign a value to a
       readonly variable, an error occurs, and the command exits with  a  non-
       zero status.

       If  no  command  name  results,  redirections are performed, but do not
       affect the current shell environment.  A redirection error  causes  the
       command to exit with a non-zero status.

       If  there is a command name left after expansion, execution proceeds as
       described below.  Otherwise, the command exits.  If one of  the  expan-
       sions  contained a command substitution, the exit status of the command
       is the exit status of the  last  command  substitution  performed.   If
       there were no command substitutions, the command exits with a status of
       zero.

COMMAND EXECUTION
       After a command has been split into words, if it results  in  a  simple
       command  and  an  optional list of arguments, the following actions are
       taken.

       If the command name contains no slashes, the shell attempts  to  locate
       it.   If  there  exists a shell function by that name, that function is
       invoked as described above in FUNCTIONS.  If the name does not match  a
       function,  the shell searches for it in the list of shell builtins.  If
       a match is found, that builtin is invoked.

       If the name is neither a shell function nor a builtin, and contains  no
       slashes,  bash  searches  each element of the PATH for a directory con-
       taining an executable file by that name.  Bash uses  a  hash  table  to
       remember  the  full pathnames of executable files (see hash under SHELL
       BUILTIN COMMANDS below).  A full search of the directories in  PATH  is
       performed  only  if the command is not found in the hash table.  If the
       search is unsuccessful, the shell prints an error message  and  returns
       an exit status of 127.

       If  the  search  is  successful, or if the command name contains one or
       more slashes, the shell executes the named program in a separate execu-
       tion environment.  Argument 0 is set to the name given, and the remain-
       ing arguments to the command are set to the arguments given, if any.

       If this execution fails because the file is not in  executable  format,
       and  the file is not a directory, it is assumed to be a shell script, a
       file containing shell commands.  A subshell is spawned to  execute  it.
       This  subshell  reinitializes itself, so that the effect is as if a new
       shell had been invoked to handle the script, with  the  exception  that
       the  locations  of  commands  remembered  by the parent (see hash below
       under SHELL BUILTIN COMMANDS) are retained by the child.

       If the program is a file beginning with ##!!, the remainder of the  first
       line  specifies an interpreter for the program.  The shell executes the
       specified interpreter on operating systems that do not handle this exe-
       cutable format themselves.  The arguments to the interpreter consist of
       a single optional argument following the interpreter name on the  first
       line  of  the program, followed by the name of the program, followed by
       the command arguments, if any.

COMMAND EXECUTION ENVIRONMENT
       The shell has an execution environment, which consists of  the  follow-
       ing:


       +o      open  files inherited by the shell at invocation, as modified by
              redirections supplied to the exec builtin

       +o      the current working directory as set by cd, pushd, or  popd,  or
              inherited by the shell at invocation

       +o      the  file  creation  mode mask as set by umask or inherited from
              the shell's parent

       +o      current traps set by trap

       +o      shell parameters that are set by variable assignment or with set
              or inherited from the shell's parent in the environment

       +o      shell  functions  defined during execution or inherited from the
              shell's parent in the environment

       +o      options enabled at invocation (either by default  or  with  com-
              mand-line arguments) or by set

       +o      options enabled by shopt

       +o      shell aliases defined with alias

       +o      various  process  IDs,  including  those of background jobs, the
              value of $$$$, and the value of $PPID

       When a simple command other than a builtin or shell function is  to  be
       executed,  it  is invoked in a separate execution environment that con-
       sists of the following.  Unless otherwise noted, the values are  inher-
       ited from the shell.


       +o      the  shell's  open  files,  plus any modifications and additions
              specified by redirections to the command

       +o      the current working directory

       +o      the file creation mode mask

       +o      shell variables and functions  marked  for  export,  along  with
              variables exported for the command, passed in the environment

       +o      traps caught by the shell are reset to the values inherited from
              the shell's parent, and traps ignored by the shell are ignored

       A command invoked  in  this  separate  environment  cannot  affect  the
       shell's execution environment.

       Command  substitution, commands grouped with parentheses, and asynchro-
       nous commands are invoked in a subshell environment that is a duplicate
       of  the  shell  environment,  except that traps caught by the shell are
       reset to the values that the shell inherited from its parent at invoca-
       tion.  Builtin commands that are invoked as part of a pipeline are also
       executed in a subshell environment.  Changes made to the subshell envi-
       ronment cannot affect the shell's execution environment.

       If  a  command  is  followed  by a && and job control is not active, the
       default standard input for the command is  the  empty  file  /dev/null.
       Otherwise,  the  invoked  command  inherits the file descriptors of the
       calling shell as modified by redirections.

ENVIRONMENT
       When a program is invoked it is given an array of  strings  called  the
       environment.   This  is  a  list  of  name-value  pairs,  of  the  form
       name=value.

       The shell provides several ways  to  manipulate  the  environment.   On
       invocation, the shell scans its own environment and creates a parameter
       for each name found, automatically marking it for export to child  pro-
       cesses.   Executed  commands  inherit  the environment.  The export and
       declare -x commands allow parameters and functions to be added  to  and
       deleted from the environment.  If the value of a parameter in the envi-
       ronment is modified, the new value becomes  part  of  the  environment,
       replacing  the  old.  The environment inherited by any executed command
       consists of the shell's initial environment, whose values may be  modi-
       fied  in  the  shell, less any pairs removed by the unset command, plus
       any additions via the export and declare -x commands.

       The environment for any simple command or  function  may  be  augmented
       temporarily  by  prefixing  it with parameter assignments, as described
       above in PARAMETERS.  These assignment statements affect only the envi-
       ronment seen by that command.

       If  the  -k option is set (see the set builtin command below), then all
       parameter assignments are placed in the environment for a command,  not
       just those that precede the command name.

       When  bash  invokes  an  external command, the variable __ is set to the
       full file name of the command and passed to that command in  its  envi-
       ronment.

EXIT STATUS
       For the shell's purposes, a command which exits with a zero exit status
       has succeeded.  An exit status of zero indicates success.   A  non-zero
       exit  status  indicates  failure.  When a command terminates on a fatal
       signal _N, bash uses the value of 128+_N as the exit status.

       If a command is not found, the child  process  created  to  execute  it
       returns  a status of 127.  If a command is found but is not executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

       Shell  builtin  commands return a status of 0 (true) if successful, and
       non-zero (false) if an error occurs while they execute.   All  builtins
       return an exit status of 2 to indicate incorrect usage.

       Bash  itself  returns  the  exit  status  of the last command executed,
       unless a syntax error occurs, in which case it exits  with  a  non-zero
       value.  See also the exit builtin command below.

SIGNALS
       When  bash  is  interactive,  in  the  absence of any traps, it ignores
       SIGTERM (so that kill 00 does not kill an interactive shell), and SIGINT
       is  caught and handled (so that the wait builtin is interruptible).  In
       all cases, bash ignores SIGQUIT.  If job control  is  in  effect,  bash
       ignores SIGTTIN, SIGTTOU, and SIGTSTP.

       Non-builtin commands run by bash have signal handlers set to the values
       inherited by the shell from its parent.  When job  control  is  not  in
       effect,  asynchronous commands ignore SIGINT and SIGQUIT in addition to
       these inherited handlers.  Commands run as a result of command  substi-
       tution ignore the keyboard-generated job control signals SIGTTIN, SIGT-
       TOU, and SIGTSTP.

       The shell exits by default upon receipt of a SIGHUP.   Before  exiting,
       an  interactive  shell  resends  the  SIGHUP  to  all  jobs, running or
       stopped.  Stopped jobs are sent SIGCONT to ensure that they receive the
       SIGHUP.   To  prevent the shell from sending the signal to a particular
       job, it should be removed from the jobs table with the  disown  builtin
       (see  SHELL  BUILTIN  COMMANDS  below)  or marked to not receive SIGHUP
       using disown -h.

       If the huponexit shell option has been set with  shopt,  bash  sends  a
       SIGHUP to all jobs when an interactive login shell exits.

       If  bash is waiting for a command to complete and receives a signal for
       which a trap has been set, the trap will not be executed until the com-
       mand  completes.   When bash is waiting for an asynchronous command via
       the wait builtin, the reception of a signal for which a trap  has  been
       set will cause the wait builtin to return immediately with an exit sta-
       tus greater than 128, immediately after which the trap is executed.

JOB CONTROL
       Job control refers to the ability to  selectively  stop  (suspend)  the
       execution of processes and continue (resume) their execution at a later
       point.  A user typically  employs  this  facility  via  an  interactive
       interface supplied jointly by the system's terminal driver and bash.

       The  shell  associates  a  job with each pipeline.  It keeps a table of
       currently executing jobs, which may be listed with  the  jobs  command.
       When  bash starts a job asynchronously (in the background), it prints a
       line that looks like:

              [1] 25647

       indicating that this job is job number 1 and that the process ID of the
       last process in the pipeline associated with this job is 25647.  All of
       the processes in a single pipeline are members of the same  job.   Bash
       uses the job abstraction as the basis for job control.

       To  facilitate the implementation of the user interface to job control,
       the operating system maintains the notion of a current terminal process
       group ID.  Members of this process group (processes whose process group
       ID is equal to the current terminal process group ID) receive keyboard-
       generated  signals  such  as SIGINT.  These processes are said to be in
       the foreground.  Background processes are those whose process group  ID
       differs from the terminal's; such processes are immune to keyboard-gen-
       erated signals.  Only foreground processes are allowed to read from  or
       write to the terminal.  Background processes which attempt to read from
       (write to) the terminal are sent a SIGTTIN (SIGTTOU) signal by the ter-
       minal driver, which, unless caught, suspends the process.

       If  the operating system on which bash is running supports job control,
       bash contains facilities to use it.  Typing the suspend character (typ-
       ically ^^ZZ, Control-Z) while a process is running causes that process to
       be stopped and returns control to bash.   Typing  the  delayed  suspend
       character  (typically  ^^YY,  Control-Y) causes the process to be stopped
       when it attempts to read input from the terminal,  and  control  to  be
       returned  to bash.  The user may then manipulate the state of this job,
       using the bg command to continue it in the background, the  fg  command
       to continue it in the foreground, or the kill command to kill it.  A ^Z
       takes effect immediately, and has the additional side effect of causing
       pending output and typeahead to be discarded.

       There are a number of ways to refer to a job in the shell.  The charac-
       ter %% introduces a job name.  Job number _n may be referred to as %%nn.  A
       job  may  also  be referred to using a prefix of the name used to start
       it, or using a substring that appears in its command line.   For  exam-
       ple, %ce refers to a stopped ce job.  If a prefix matches more than one
       job, bash reports an error.  Using %?ce, on the other hand,  refers  to
       any job containing the string ce in its command line.  If the substring
       matches more than one job, bash reports an error.  The symbols  %%%%  and
       %%++  refer  to  the shell's notion of the current job, which is the last
       job stopped while it was in the foreground  or  started  in  the  back-
       ground.   The  previous job may be referenced using %%--.  In output per-
       taining to jobs (e.g., the output of the jobs command), the current job
       is  always flagged with a ++, and the previous job with a --.  A single %
       (with no accompanying job specification) also  refers  to  the  current
       job.

       Simply  naming a job can be used to bring it into the foreground: %%11 is
       a synonym for ``fg %%11'''', bringing job 1 from the  background  into  the
       foreground.   Similarly,  ````%%11  &&''''  resumes  job  1 in the background,
       equivalent to ``bg %%11''''.

       The shell learns immediately whenever a job changes  state.   Normally,
       bash waits until it is about to print a prompt before reporting changes
       in a job's status so as to not interrupt any other output.  If  the  -b
       option to the set builtin command is enabled, bash reports such changes
       immediately.  Any trap on SIGCHLD  is  executed  for  each  child  that
       exits.

       If  an  attempt  to exit bash is made while jobs are stopped, the shell
       prints a warning message.  The jobs command may then be used to inspect
       their status.  If a second attempt to exit is made without an interven-
       ing command, the shell does not print another warning, and the  stopped
       jobs are terminated.

PROMPTING
       When executing interactively, bash displays the primary prompt PS1 when
       it is ready to read a command, and the secondary  prompt  PS2  when  it
       needs  more  input  to  complete  a  command.  Bash allows these prompt
       strings to be customized by inserting  a  number  of  backslash-escaped
       special characters that are decoded as follows:
              \a     an ASCII bell character (07)
              \d     the  date  in "Weekday Month Date" format (e.g., "Tue May
                     26")
              \D{format}}
                     the format is passed to strftime(3)  and  the  result  is
                     inserted  into the prompt string; an empty format results
                     in a locale-specific time representation.  The braces are
                     required
              \e     an ASCII escape character (033)
              \h     the hostname up to the first `.'
              \H     the hostname
              \j     the number of jobs currently managed by the shell
              \l     the basename of the shell's terminal device name
              \n     newline
              \r     carriage return
              \s     the  name  of  the shell, the basename of $$00 (the portion
                     following the final slash)
              \t     the current time in 24-hour HH:MM:SS format
              \T     the current time in 12-hour HH:MM:SS format
              \\@@     the current time in 12-hour am/pm format
              \A     the current time in 24-hour HH:MM format
              \u     the username of the current user
              \v     the version of bash (e.g., 2.00)
              \V     the release of bash, version + patch level (e.g., 2.00.0)
              \w     the  current  working  directory,  with $HOME abbreviated
                     with a tilde
              \W     the basename of the current working directory, with $HOME
                     abbreviated with a tilde
              \\!!     the history number of this command
              \\##     the command number of this command
              \\$$     if the effective UID is 0, a ##, otherwise a $$
              \\nnn   the character corresponding to the octal number nnn
              \\\\     a backslash
              \\[[     begin  a sequence of non-printing characters, which could
                     be used to embed a terminal  control  sequence  into  the
                     prompt
              \\]]     end a sequence of non-printing characters

       The  command  number  and the history number are usually different: the
       history number of a command is its position in the history list,  which
       may  include  commands  restored  from  the  history  file (see HISTORY
       below), while the command number is the position  in  the  sequence  of
       commands  executed  during the current shell session.  After the string
       is decoded, it is expanded via parameter expansion,  command  substitu-
       tion,  arithmetic expansion, and quote removal, subject to the value of
       the promptvars shell option (see the description of the  shopt  command
       under SHELL BUILTIN COMMANDS below).

READLINE
       This  is  the library that handles reading input when using an interac-
       tive shell, unless the --noediting option is given at shell invocation.
       By default, the line editing commands are similar to those of emacs.  A
       vi-style line editing interface is also available.  To  turn  off  line
       editing  after  the shell is running, use the +o emacs or +o vi options
       to the set builtin (see SHELL BUILTIN COMMANDS below).

   Readline Notation
       In this section, the emacs-style notation is used to denote keystrokes.
       Control  keys  are  denoted by C-key, e.g., C-n means Control-N.  Simi-
       larly, meta keys are denoted by M-key, so M-x means Meta-X.   (On  key-
       boards  without a meta key, M-_x means ESC _x, i.e., press the Escape key
       then the _x key.  This makes ESC the meta prefix.  The combination M-C-_x
       means  ESC-Control-_x, or press the Escape key then hold the Control key
       while pressing the _x key.)

       Readline commands may be given numeric arguments, which normally act as
       a  repeat  count.   Sometimes,  however, it is the sign of the argument
       that is significant.  Passing a negative argument  to  a  command  that
       acts  in the forward direction (e.g., kill-line) causes that command to
       act in a backward direction.  Commands whose  behavior  with  arguments
       deviates from this are noted below.

       When  a command is described as killing text, the text deleted is saved
       for possible future retrieval (yanking).  The killed text is saved in a
       kill ring.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

   Readline Initialization
       Readline  is  customized  by putting commands in an initialization file
       (the inputrc file).  The name of this file is taken from the  value  of
       the  INPUTRC  variable.   If  that  variable  is  unset, the default is
       ~/.inputrc.  When a program which uses the readline library starts  up,
       the initialization file is read, and the key bindings and variables are
       set.  There are only a few basic constructs  allowed  in  the  readline
       initialization  file.  Blank lines are ignored.  Lines beginning with a
       ## are comments.  Lines beginning with a  $$  indicate  conditional  con-
       structs.  Other lines denote key bindings and variable settings.

       The  default  key-bindings  may be changed with an inputrc file.  Other
       programs that use this library may add their own commands and bindings.

       For example, placing

              M-Control-u: universal-argument
       or
              C-Meta-u: universal-argument
       into  the inputrc would make M-C-u execute the readline command univer-
       sal-argument.

       The following symbolic character names  are  recognized:  RUBOUT,  DEL,
       ESC, LFD, NEWLINE, RET, RETURN, SPC, SPACE, and TAB.

       In  addition  to  command  names, readline allows keys to be bound to a
       string that is inserted when the key is pressed (a macro).

   Readline Key Bindings
       The syntax for controlling key bindings in the inputrc file is  simple.
       All  that is required is the name of the command or the text of a macro
       and a key sequence to which it should be bound. The name may be  speci-
       fied in one of two ways: as a symbolic key name, possibly with Meta- or
       Control- prefixes, or as a key sequence.

       When using the form keyname:function-name or macro, keyname is the name
       of a key spelled out in English.  For example:

              Control-u: universal-argument
              Meta-Rubout: backward-kill-word
              Control-o: "> output"

       In  the above example, C-u is bound to the function universal-argument,
       M-DEL is bound to the function backward-kill-word, and C-o is bound  to
       run  the macro expressed on the right hand side (that is, to insert the
       text ``> output'' into the line).

       In the second form, "keyseq":function-name  or  macro,  keyseq  differs
       from  keyname above in that strings denoting an entire key sequence may
       be specified by placing the sequence within double  quotes.   Some  GNU
       Emacs  style  key escapes can be used, as in the following example, but
       the symbolic character names are not recognized.

              "\C-u": universal-argument
              "\C-x\C-r": re-read-init-file
              "\e[11~": "Function Key 1"

       In this example, C-u is again bound to the function universal-argument.
       C-x  C-r is bound to the function re-read-init-file, and ESC _[ _1 _1 _~ is
       bound to insert the text ``Function Key 1''.

       The full set of GNU Emacs style escape sequences is
              \C-    control prefix
              \M-    meta prefix
              \e     an escape character
              \\\\     backslash
              \\""     literal "
              \\''     literal '

       In addition to the GNU Emacs style escape sequences, a  second  set  of
       backslash escapes is available:
              \a     alert (bell)
              \b     backspace
              \d     delete
              \f     form feed
              \n     newline
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\nnn   the  eight-bit  character  whose value is the octal value
                     nnn (one to three digits)
              \\xx_H_H   the eight-bit character whose value  is  the  hexadecimal
                     value HH (one or two hex digits)

       When entering the text of a macro, single or double quotes must be used
       to indicate a macro definition.  Unquoted text is assumed to be a func-
       tion  name.   In  the macro body, the backslash escapes described above
       are expanded.  Backslash will quote any other character  in  the  macro
       text, including " and '.

       Bash  allows the current readline key bindings to be displayed or modi-
       fied with the bind builtin command.  The editing mode may  be  switched
       during  interactive  use by using the -o option to the set builtin com-
       mand (see SHELL BUILTIN COMMANDS below).

   Readline Variables
       Readline has variables that can be used to further customize its behav-
       ior.  A variable may be set in the inputrc file with a statement of the
       form

              set variable-name value

       Except where noted, readline variables can take the values  On  or  Off
       (without  regard  to  case).   Unrecognized variable names are ignored.
       When a variable value is read, empty or null values, "on"  (case-insen-
       sitive), and "1" are equivalent to On.  All other values are equivalent
       to Off.  The variables and their default values are:

       bell-style (audible)
              Controls what happens when readline wants to ring  the  terminal
              bell.  If set to none, readline never rings the bell.  If set to
              visible, readline uses a visible bell if one is  available.   If
              set to audible, readline attempts to ring the terminal's bell.
       bind-tty-special-chars (On)
              If  set  to On, readline attempts to bind the control characters
              treated specially by the kernel's terminal driver to their read-
              line equivalents.
       comment-begin ((````##''''))
              The  string  that  is  inserted when the readline insert-comment
              command is executed.  This command is bound to M-# in emacs mode
              and to ## in vi command mode.
       completion-ignore-case (Off)
              If set to On, readline performs filename matching and completion
              in a case-insensitive fashion.
       completion-query-items ((110000))
              This determines when the user is queried about viewing the  num-
              ber  of  possible  completions generated by the possible-comple-
              tions command.  It may be set to any integer value greater  than
              or  equal  to  zero.   If  the number of possible completions is
              greater than or equal to the value of this variable, the user is
              asked  whether or not he wishes to view them; otherwise they are
              simply listed on the terminal.
       convert-meta (On)
              If set to On, readline will convert characters with  the  eighth
              bit set to an ASCII key sequence by stripping the eighth bit and
              prefixing an escape character (in effect, using  escape  as  the
              meta prefix).
       disable-completion (Off)
              If set to On, readline will inhibit word completion.  Completion
              characters will be inserted into the line as if  they  had  been
              mapped to self-insert.
       editing-mode (emacs)
              Controls whether readline begins with a set of key bindings sim-
              ilar to emacs or vi.  editing-mode can be set to either emacs or
              vi.
       enable-keypad (Off)
              When set to On, readline will try to enable the application key-
              pad when it is called.  Some systems need  this  to  enable  the
              arrow keys.
       expand-tilde (Off)
              If  set  to  on,  tilde  expansion  is  performed  when readline
              attempts word completion.
       history-preserve-point (Off)
              If set to on, the history code attempts to place  point  at  the
              same  location on each history line retrieved with previous-his-
              tory or next-history.
       horizontal-scroll-mode (Off)
              When set to On, makes readline use a single  line  for  display,
              scrolling the input horizontally on a single screen line when it
              becomes longer than the screen width rather than wrapping  to  a
              new line.
       input-meta (Off)
              If  set to On, readline will enable eight-bit input (that is, it
              will not strip the high  bit  from  the  characters  it  reads),
              regardless of what the terminal claims it can support.  The name
              meta-flag is a synonym for this variable.
       isearch-terminators (``C-[C-J'')
              The string of characters that should  terminate  an  incremental
              search  without  subsequently  executing the character as a com-
              mand.  If this variable has not been given a value, the  charac-
              ters ESC and C-J will terminate an incremental search.
       keymap (emacs)
              Set  the current readline keymap.  The set of valid keymap names
              is emacs, emacs-standard, emacs-meta,  emacs-ctlx,  vi,  vi-com-
              mand,  and  vi-insert.  vi is equivalent to vi-command; emacs is
              equivalent to emacs-standard.  The default value is  emacs;  the
              value of editing-mode also affects the default keymap.
       mark-directories (On)
              If set to On, completed directory names have a slash appended.
       mark-modified-lines (Off)
              If  set  to  On,  history lines that have been modified are dis-
              played with a preceding asterisk (**).
       mark-symlinked-directories (Off)
              If set to On, completed names which are symbolic links to direc-
              tories   have   a  slash  appended  (subject  to  the  value  of
              mark-directories).
       match-hidden-files (On)
              This variable, when set to On, causes readline  to  match  files
              whose  names  begin  with  a  `.' (hidden files) when performing
              filename completion, unless the leading `.' is supplied  by  the
              user in the filename to be completed.
       output-meta (Off)
              If  set  to On, readline will display characters with the eighth
              bit set directly rather than as a meta-prefixed escape sequence.
       page-completions (On)
              If  set to On, readline uses an internal more-like pager to dis-
              play a screenful of possible completions at a time.
       print-completions-horizontally (Off)
              If set to On, readline will  display  completions  with  matches
              sorted  horizontally in alphabetical order, rather than down the
              screen.
       show-all-if-ambiguous (Off)
              This alters the default behavior of  the  completion  functions.
              If set to on, words which have more than one possible completion
              cause the matches to be listed immediately  instead  of  ringing
              the bell.
       show-all-if-unmodified (Off)
              This  alters the default behavior of the completion functions in
              a fashion similar to show-all-if-ambiguous.  If set to on, words
              which  have more than one possible completion without any possi-
              ble partial completion (the possible completions don't  share  a
              common  prefix)  cause  the  matches  to  be  listed immediately
              instead of ringing the bell.
       visible-stats (Off)
              If set to On, a character denoting a file's type as reported  by
              stat(2)  is  appended to the filename when listing possible com-
              pletions.

   Readline Conditional Constructs
       Readline implements a facility similar in  spirit  to  the  conditional
       compilation  features  of  the C preprocessor which allows key bindings
       and variable settings to be performed as the result  of  tests.   There
       are four parser directives used.

       $if    The  $if construct allows bindings to be made based on the edit-
              ing mode, the terminal being  used,  or  the  application  using
              readline.   The text of the test extends to the end of the line;
              no characters are required to isolate it.

              mode   The mode= form of the  $if  directive  is  used  to  test
                     whether  readline  is  in  emacs or vi mode.  This may be
                     used in conjunction with  the  set  keymap  command,  for
                     instance,  to  set  bindings  in  the  emacs-standard and
                     emacs-ctlx keymaps only if readline is  starting  out  in
                     emacs mode.

              term   The  term=  form may be used to include terminal-specific
                     key bindings, perhaps to bind the key sequences output by
                     the terminal's function keys.  The word on the right side
                     of the == is tested against the both full name of the ter-
                     minal  and  the  portion  of the terminal name before the
                     first --.  This allows sun to match both sun and  sun-cmd,
                     for instance.

              application
                     The application construct is used to include application-
                     specific  settings.   Each  program  using  the  readline
                     library  sets the application name, and an initialization
                     file can test for a particular value.  This could be used
                     to  bind key sequences to functions useful for a specific
                     program.  For instance, the following command adds a  key
                     sequence  that  quotes  the  current  or previous word in
                     Bash:

                     $if Bash
                     # Quote the current or previous word
                     "\C-xq": "\eb\"\ef\""
                     $endif

       $endif This command, as seen in the previous example, terminates an $if
              command.

       $else  Commands in this branch of the $if directive are executed if the
              test fails.

       $include
              This directive takes a single filename as an argument and  reads
              commands  and bindings from that file.  For example, the follow-
              ing directive would read /etc/inputrc:

              $include  /etc/inputrc

   Searching
       Readline provides commands for searching through  the  command  history
       (see HISTORY below) for lines containing a specified string.  There are
       two search modes: incremental and non-incremental.

       Incremental searches begin before the  user  has  finished  typing  the
       search  string.  As each character of the search string is typed, read-
       line displays the next entry from the history matching the string typed
       so  far.   An  incremental  search  requires only as many characters as
       needed to find the desired history entry.  The  characters  present  in
       the  value of the isearch-terminators variable are used to terminate an
       incremental search.  If that variable has not been assigned a value the
       Escape  and  Control-J characters will terminate an incremental search.
       Control-G will abort an incremental search  and  restore  the  original
       line.   When the search is terminated, the history entry containing the
       search string becomes the current line.

       To find other matching entries in the history list, type  Control-S  or
       Control-R  as appropriate.  This will search backward or forward in the
       history for the next entry matching the search  string  typed  so  far.
       Any  other  key sequence bound to a readline command will terminate the
       search and execute that command.  For instance, a newline  will  termi-
       nate the search and accept the line, thereby executing the command from
       the history list.

       Readline remembers the last incremental search string.  If two Control-
       Rs  are  typed without any intervening characters defining a new search
       string, any remembered search string is used.

       Non-incremental searches read the entire search string before  starting
       to  search  for matching history lines.  The search string may be typed
       by the user or be part of the contents of the current line.

   Readline Command Names
       The following is a list of the names of the commands  and  the  default
       key sequences to which they are bound.  Command names without an accom-
       panying key sequence are unbound by default.  In the following descrip-
       tions,  point refers to the current cursor position, and mark refers to
       a cursor position saved by the set-mark command.  The text between  the
       point and mark is referred to as the region.

   Commands for Moving
       beginning-of-line (C-a)
              Move to the start of the current line.
       end-of-line (C-e)
              Move to the end of the line.
       forward-char (C-f)
              Move forward a character.
       backward-char (C-b)
              Move back a character.
       forward-word (M-f)
              Move forward to the end of the next word.  Words are composed of
              alphanumeric characters (letters and digits).
       backward-word (M-b)
              Move back to the start of the current or previous  word.   Words
              are composed of alphanumeric characters (letters and digits).
       clear-screen (C-l)
              Clear  the  screen  leaving  the  current line at the top of the
              screen.  With an argument,  refresh  the  current  line  without
              clearing the screen.
       redraw-current-line
              Refresh the current line.

   Commands for Manipulating the History
       accept-line (Newline, Return)
              Accept the line regardless of where the cursor is.  If this line
              is non-empty, add it to the history list according to the  state
              of  the HISTCONTROL variable.  If the line is a modified history
              line, then restore the history line to its original state.
       previous-history (C-p)
              Fetch the previous command from the history list, moving back in
              the list.
       next-history (C-n)
              Fetch  the next command from the history list, moving forward in
              the list.
       beginning-of-history (M-<)
              Move to the first line in the history.
       end-of-history (M->)
              Move to the end of the input history, i.e., the  line  currently
              being entered.
       reverse-search-history (C-r)
              Search  backward  starting  at  the current line and moving `up'
              through the  history  as  necessary.   This  is  an  incremental
              search.
       forward-search-history (C-s)
              Search  forward  starting  at the current line and moving `down'
              through the  history  as  necessary.   This  is  an  incremental
              search.
       non-incremental-reverse-search-history (M-p)
              Search backward through the history starting at the current line
              using a non-incremental search for  a  string  supplied  by  the
              user.
       non-incremental-forward-search-history (M-n)
              Search  forward  through  the  history  using  a non-incremental
              search for a string supplied by the user.
       history-search-forward
              Search forward through the history for the string of  characters
              between  the start of the current line and the point.  This is a
              non-incremental search.
       history-search-backward
              Search backward through the history for the string of characters
              between  the start of the current line and the point.  This is a
              non-incremental search.
       yank-nth-arg (M-C-y)
              Insert the first argument to the previous command  (usually  the
              second word on the previous line) at point.  With an argument _n,
              insert the _nth word from the previous command (the words in  the
              previous  command  begin  with  word  0).   A  negative argument
              inserts the _nth word from the end of the previous command.  Once
              the  argument _n is computed, the argument is extracted as if the
              "!_n" history expansion had been specified.
       yank-last-arg (M-., M-_)
              Insert the last argument to the previous command (the last  word
              of  the  previous  history  entry).   With  an  argument, behave
              exactly like yank-nth-arg.  Successive  calls  to  yank-last-arg
              move  back through the history list, inserting the last argument
              of each line in turn.  The history expansion facilities are used
              to  extract  the last argument, as if the "!$" history expansion
              had been specified.
       shell-expand-line (M-C-e)
              Expand the line as the shell does.  This performs alias and his-
              tory expansion as well as all of the shell word expansions.  See
              HISTORY EXPANSION below for a description of history  expansion.
       history-expand-line (M-^)
              Perform  history  expansion  on  the  current line.  See HISTORY
              EXPANSION below for a description of history expansion.
       magic-space
              Perform history expansion on  the  current  line  and  insert  a
              space.  See HISTORY EXPANSION below for a description of history
              expansion.
       alias-expand-line
              Perform alias expansion on the current line.  See ALIASES  above
              for a description of alias expansion.
       history-and-alias-expand-line
              Perform history and alias expansion on the current line.
       insert-last-argument (M-., M-_)
              A synonym for yank-last-arg.
       operate-and-get-next (C-o)
              Accept  the  current  line for execution and fetch the next line
              relative to the current line from the history for editing.   Any
              argument is ignored.
       edit-and-execute-command (C-xC-e)
              Invoke  an  editor  on the current command line, and execute the
              result as shell commands.   Bash  attempts  to  invoke  $FCEDIT,
              $EDITOR, and emacs as the editor, in that order.

   Commands for Changing Text
       delete-char (C-d)
              Delete  the character at point.  If point is at the beginning of
              the line, there are no characters in  the  line,  and  the  last
              character typed was not bound to delete-char, then return EOF.
       backward-delete-char (Rubout)
              Delete  the  character  behind the cursor.  When given a numeric
              argument, save the deleted text on the kill ring.
       forward-backward-delete-char
              Delete the character under the cursor, unless the cursor  is  at
              the end of the line, in which case the character behind the cur-
              sor is deleted.
       quoted-insert (C-q, C-v)
              Add the next character typed to the line verbatim.  This is  how
              to insert characters like C-q, for example.
       tab-insert (C-v TAB)
              Insert a tab character.
       self-insert (a, b, A, 11,, !!,, ......))
              Insert the character typed.
       transpose-chars (C-t)
              Drag  the  character  before point forward over the character at
              point, moving point forward as well.  If point is at the end  of
              the  line, then this transposes the two characters before point.
              Negative arguments have no effect.
       transpose-words (M-t)
              Drag the word before point past the  word  after  point,  moving
              point  over  that  word  as well.  If point is at the end of the
              line, this transposes the last two words on the line.
       upcase-word (M-u)
              Uppercase the current (or  following)  word.   With  a  negative
              argument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
              Lowercase  the  current  (or  following)  word.  With a negative
              argument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following)  word.   With  a  negative
              argument, capitalize the previous word, but do not move point.
       overwrite-mode
              Toggle  overwrite mode.  With an explicit positive numeric argu-
              ment, switches to overwrite mode.  With an explicit non-positive
              numeric argument, switches to insert mode.  This command affects
              only emacs mode; vi mode does overwrite differently.  Each  call
              to readline() starts in insert mode.  In overwrite mode, charac-
              ters bound to self-insert replace the text at point rather  than
              pushing  the  text  to  the  right.   Characters  bound to back-
              ward-delete-char replace  the  character  before  point  with  a
              space.  By default, this command is unbound.

   Killing and Yanking
       kill-line (C-k)
              Kill the text from point to the end of the line.
       backward-kill-line (C-x Rubout)
              Kill backward to the beginning of the line.
       unix-line-discard (C-u)
              Kill  backward  from  point  to  the beginning of the line.  The
              killed text is saved on the kill-ring.
       kill-whole-line
              Kill all characters on the current line, no matter  where  point
              is.
       kill-word (M-d)
              Kill  from  point  to the end of the current word, or if between
              words, to the end of the next word.   Word  boundaries  are  the
              same as those used by forward-word.
       backward-kill-word (M-Rubout)
              Kill  the  word  behind  point.  Word boundaries are the same as
              those used by backward-word.
       unix-word-rubout (C-w)
              Kill the word behind point, using white space as a  word  bound-
              ary.  The killed text is saved on the kill-ring.
       unix-filename-rubout
              Kill  the  word  behind  point,  using white space and the slash
              character as the word boundaries.  The killed text is  saved  on
              the kill-ring.
       delete-horizontal-space (M-\)
              Delete all spaces and tabs around point.
       kill-region
              Kill the text in the current region.
       copy-region-as-kill
              Copy the text in the region to the kill buffer.
       copy-backward-word
              Copy  the word before point to the kill buffer.  The word bound-
              aries are the same as backward-word.
       copy-forward-word
              Copy the word following point to  the  kill  buffer.   The  word
              boundaries are the same as forward-word.
       yank (C-y)
              Yank the top of the kill ring into the buffer at point.
       yank-pop (M-y)
              Rotate  the kill ring, and yank the new top.  Only works follow-
              ing yank or yank-pop.

   Numeric Arguments
       digit-argument (M-0, M-1, ......,, M--)
              Add this digit to the argument already accumulating, or start  a
              new argument.  M-- starts a negative argument.
       universal-argument
              This  is another way to specify an argument.  If this command is
              followed by one or more digits, optionally with a leading  minus
              sign,  those digits define the argument.  If the command is fol-
              lowed by digits, executing  universal-argument  again  ends  the
              numeric  argument, but is otherwise ignored.  As a special case,
              if this command is immediately followed by a character  that  is
              neither  a  digit or minus sign, the argument count for the next
              command is multiplied by four.  The argument count is  initially
              one,  so  executing this function the first time makes the argu-
              ment count four, a second time makes the argument count sixteen,
              and so on.

   Completing
       complete (TAB)
              Attempt  to  perform  completion on the text before point.  Bash
              attempts completion treating the text as a variable (if the text
              begins  with  $$), username (if the text begins with ~~), hostname
              (if the text begins with @@), or command (including  aliases  and
              functions) in turn.  If none of these produces a match, filename
              completion is attempted.
       possible-completions (M-?)
              List the possible completions of the text before point.
       insert-completions (M-*)
              Insert all completions of the text before point that would  have
              been generated by possible-completions.
       menu-complete
              Similar  to complete, but replaces the word to be completed with
              a single match from the list of possible completions.   Repeated
              execution  of  menu-complete  steps through the list of possible
              completions, inserting each match in turn.  At the  end  of  the
              list of completions, the bell is rung (subject to the setting of
              bell-style) and the original text is restored.  An argument of _n
              moves  _n  positions  forward  in the list of matches; a negative
              argument may be used to move backward through  the  list.   This
              command  is  intended  to  be  bound  to  TAB, but is unbound by
              default.
       delete-char-or-list
              Deletes the character under the cursor if not at  the  beginning
              or  end  of  the  line (like delete-char).  If at the end of the
              line, behaves identically to possible-completions.  This command
              is unbound by default.
       complete-filename (M-/)
              Attempt filename completion on the text before point.
       possible-filename-completions (C-x //))
              List the possible completions of the text before point, treating
              it as a filename.
       complete-username (M-~)
              Attempt completion on the text before point, treating  it  as  a
              username.
       possible-username-completions (C-x ~~))
              List the possible completions of the text before point, treating
              it as a username.
       complete-variable (M-$)
              Attempt completion on the text before point, treating  it  as  a
              shell variable.
       possible-variable-completions (C-x $$))
              List the possible completions of the text before point, treating
              it as a shell variable.
       complete-hostname (M-@)
              Attempt completion on the text before point, treating  it  as  a
              hostname.
       possible-hostname-completions (C-x @@))
              List the possible completions of the text before point, treating
              it as a hostname.
       complete-command (M-!)
              Attempt completion on the text before point, treating  it  as  a
              command  name.   Command  completion  attempts to match the text
              against  aliases,  reserved  words,   shell   functions,   shell
              builtins, and finally executable filenames, in that order.
       possible-command-completions (C-x !!))
              List the possible completions of the text before point, treating
              it as a command name.
       dynamic-complete-history (M-TAB)
              Attempt completion on the text before point, comparing the  text
              against  lines  from  the  history  list for possible completion
              matches.
       complete-into-braces (M-{)
              Perform filename completion and insert the list of possible com-
              pletions  enclosed within braces so the list is available to the
              shell (see Brace Expansion above).

   Keyboard Macros
       start-kbd-macro (C-x (())
              Begin saving the characters  typed  into  the  current  keyboard
              macro.
       end-kbd-macro (C-x ))))
              Stop saving the characters typed into the current keyboard macro
              and store the definition.
       call-last-kbd-macro (C-x e)
              Re-execute the last keyboard macro defined, by making the  char-
              acters in the macro appear as if typed at the keyboard.

   Miscellaneous
       re-read-init-file (C-x C-r)
              Read  in  the  contents of the inputrc file, and incorporate any
              bindings or variable assignments found there.
       abort (C-g)
              Abort the current editing command and ring the  terminal's  bell
              (subject to the setting of bell-style).
       do-uppercase-version (M-a, M-b, MM--_x,, ......))
              If  the  metafied character _x is lowercase, run the command that
              is bound to the corresponding uppercase character.
       prefix-meta (ESC)
              Metafy the next character typed.  ESC ff is equivalent to Meta-f.
       undo (C-_, C-x C-u)
              Incremental undo, separately remembered for each line.
       revert-line (M-r)
              Undo  all changes made to this line.  This is like executing the
              undo command enough times to return  the  line  to  its  initial
              state.
       tilde-expand (M-&)
              Perform tilde expansion on the current word.
       set-mark (C-@, M-<space>)
              Set  the  mark to the point.  If a numeric argument is supplied,
              the mark is set to that position.
       exchange-point-and-mark (C-x C-x)
              Swap the point with the mark.  The current  cursor  position  is
              set  to the saved position, and the old cursor position is saved
              as the mark.
       character-search (C-])
              A character is read and point is moved to the next occurrence of
              that  character.   A negative count searches for previous occur-
              rences.
       character-search-backward (M-C-])
              A character is read and point is moved to  the  previous  occur-
              rence  of  that character.  A negative count searches for subse-
              quent occurrences.
       insert-comment (M-#)
              Without a numeric argument,  the  value  of  the  readline  com-
              ment-begin  variable is inserted at the beginning of the current
              line.  If a numeric argument is supplied, this command acts as a
              toggle:   if  the characters at the beginning of the line do not
              match the value of comment-begin, the value is inserted,  other-
              wise the characters in comment-begin are deleted from the begin-
              ning of the line.  In either case, the line is accepted as if  a
              newline  had  been  typed.   The  default value of comment-begin
              causes this command to make the current line  a  shell  comment.
              If  a  numeric  argument  causes  the  comment  character  to be
              removed, the line will be executed by the shell.
       glob-complete-word (M-g)
              The word before point is  treated  as  a  pattern  for  pathname
              expansion,  with  an asterisk implicitly appended.  This pattern
              is used to generate a list of matching file names  for  possible
              completions.
       glob-expand-word (C-x **))
              The  word  before  point  is  treated  as a pattern for pathname
              expansion, and the list of  matching  file  names  is  inserted,
              replacing  the  word.   If  a  numeric  argument is supplied, an
              asterisk is appended before pathname expansion.
       glob-list-expansions (C-x g)
              The list  of  expansions  that  would  have  been  generated  by
              glob-expand-word  is  displayed,  and the line is redrawn.  If a
              numeric argument is supplied, an  asterisk  is  appended  before
              pathname expansion.
       dump-functions
              Print  all  of the functions and their key bindings to the read-
              line output stream.  If a numeric argument is supplied, the out-
              put  is  formatted  in such a way that it can be made part of an
              inputrc file.
       dump-variables
              Print all of the settable readline variables and their values to
              the  readline output stream.  If a numeric argument is supplied,
              the output is formatted in such a way that it can be  made  part
              of an inputrc file.
       dump-macros
              Print  all of the readline key sequences bound to macros and the
              strings they output.  If a numeric  argument  is  supplied,  the
              output is formatted in such a way that it can be made part of an
              inputrc file.
       display-shell-version (C-x C-v)
              Display version information about the current instance of  bash.

   Programmable Completion
       When  word  completion  is  attempted  for an argument to a command for
       which a completion specification (a compspec) has  been  defined  using
       the  complete  builtin  (see  SHELL  BUILTIN  COMMANDS below), the pro-
       grammable completion facilities are invoked.

       First, the command name is identified.  If a compspec has been  defined
       for that command, the compspec is used to generate the list of possible
       completions for the word.  If the command word is a  full  pathname,  a
       compspec  for  the full pathname is searched for first.  If no compspec
       is found for the full pathname, an attempt is made to find  a  compspec
       for the portion following the final slash.

       Once  a  compspec  has  been  found, it is used to generate the list of
       matching words.  If a compspec is not found, the default  bash  comple-
       tion as described above under Completing is performed.

       First,  the  actions  specified by the compspec are used.  Only matches
       which are prefixed by the word being completed are returned.  When  the
       -f  or -d option is used for filename or directory name completion, the
       shell variable FIGNORE is used to filter the matches.

       Any completions specified by a filename expansion  pattern  to  the  -G
       option are generated next.  The words generated by the pattern need not
       match the word being completed.  The GLOBIGNORE shell variable  is  not
       used to filter the matches, but the FIGNORE variable is used.

       Next,  the string specified as the argument to the -W option is consid-
       ered.  The string is first split using the characters in the  IFS  spe-
       cial  variable  as delimiters.  Shell quoting is honored.  Each word is
       then expanded using brace expansion,  tilde  expansion,  parameter  and
       variable  expansion, command substitution, and arithmetic expansion, as
       described above under EXPANSION.  The results are split using the rules
       described above under Word Splitting.  The results of the expansion are
       prefix-matched against the word being completed, and the matching words
       become the possible completions.

       After  these matches have been generated, any shell function or command
       specified with the -F and -C options is invoked.  When the  command  or
       function  is  invoked,  the  COMP_LINE  and  COMP_POINT  variables  are
       assigned values as described above under Shell Variables.  If  a  shell
       function  is being invoked, the COMP_WORDS and COMP_CWORD variables are
       also set.  When the function or command is invoked, the first  argument
       is  the  name  of  the command whose arguments are being completed, the
       second argument is the word being completed, and the third argument  is
       the  word  preceding  the  word  being completed on the current command
       line.  No filtering of the generated completions against the word being
       completed is performed; the function or command has complete freedom in
       generating the matches.

       Any function specified with -F is invoked first.  The function may  use
       any  of  the  shell facilities, including the compgen builtin described
       below, to generate the matches.  It must put the  possible  completions
       in the COMPREPLY array variable.

       Next,  any  command specified with the -C option is invoked in an envi-
       ronment equivalent to command substitution.  It should print a list  of
       completions,  one  per  line, to the standard output.  Backslash may be
       used to escape a newline, if necessary.

       After all of the possible completions are generated, any filter  speci-
       fied  with  the -X option is applied to the list.  The filter is a pat-
       tern as used for pathname expansion; a && in  the  pattern  is  replaced
       with  the text of the word being completed.  A literal && may be escaped
       with a backslash; the backslash is removed before attempting  a  match.
       Any  completion that matches the pattern will be removed from the list.
       A leading !! negates the pattern; in this case any completion not match-
       ing the pattern will be removed.

       Finally, any prefix and suffix specified with the -P and -S options are
       added to each member of the completion list, and the result is returned
       to the readline completion code as the list of possible completions.

       If  the previously-applied actions do not generate any matches, and the
       -o dirnames option was supplied  to  complete  when  the  compspec  was
       defined, directory name completion is attempted.

       If  the  -o  plusdirs option was supplied to complete when the compspec
       was defined, directory name completion is attempted and any matches are
       added to the results of the other actions.

       By  default,  if a compspec is found, whatever it generates is returned
       to the completion code as the full set of  possible  completions.   The
       default bash completions are not attempted, and the readline default of
       filename completion is disabled.  If the -o bashdefault option was sup-
       plied  to complete when the compspec was defined, the bash default com-
       pletions are attempted if the compspec generates no matches.  If the -o
       default  option was supplied to complete when the compspec was defined,
       readline's default completion will be performed if the  compspec  (and,
       if attempted, the default bash completions) generate no matches.

       When  a  compspec  indicates that directory name completion is desired,
       the programmable completion functions force readline to append a  slash
       to  completed names which are symbolic links to directories, subject to
       the value of the mark-directories readline variable, regardless of  the
       setting of the mark-symlinked-directories readline variable.

HISTORY
       When  the  -o  history  option to the set builtin is enabled, the shell
       provides access to the command history, the list of commands previously
       typed.   The  value  of  the HISTSIZE variable is used as the number of
       commands to save in a history list.  The text of the last HISTSIZE com-
       mands  (default  500)  is  saved.  The shell stores each command in the
       history list prior to parameter and variable expansion  (see  EXPANSION
       above)  but after history expansion is performed, subject to the values
       of the shell variables HISTIGNORE and HISTCONTROL.

       On startup, the history is initialized from the file named by the vari-
       able  HISTFILE  (default ~/.bash__history).  The file named by the value
       of HISTFILE is truncated, if necessary, to contain  no  more  than  the
       number of lines specified by the value of HISTFILESIZE.  When an inter-
       active shell exits, the last $HISTSIZE lines are copied from  the  his-
       tory list to $HISTFILE.  If the histappend shell option is enabled (see
       the description of shopt under SHELL BUILTIN COMMANDS below), the lines
       are  appended  to the history file, otherwise the history file is over-
       written.  If HISTFILE is unset, or if the history file  is  unwritable,
       the  history  is not saved.  After saving the history, the history file
       is truncated to contain no more than HISTFILESIZE lines.  If  HISTFILE-
       SIZE is not set, no truncation is performed.

       The  builtin  command fc (see SHELL BUILTIN COMMANDS below) may be used
       to list or edit and re-execute a portion of the history list.  The his-
       tory  builtin  may  be  used  to display or modify the history list and
       manipulate the history file.  When using command-line  editing,  search
       commands  are available in each editing mode that provide access to the
       history list.

       The shell allows control over which commands are saved on  the  history
       list.  The HISTCONTROL and HISTIGNORE variables may be set to cause the
       shell to save only a subset of the commands entered.  The cmdhist shell
       option,  if enabled, causes the shell to attempt to save each line of a
       multi-line command in the same history entry, adding  semicolons  where
       necessary  to preserve syntactic correctness.  The lithist shell option
       causes the shell to save the command with embedded newlines instead  of
       semicolons.  See the description of the shopt builtin below under SHELL
       BUILTIN  COMMANDS  for  information  on  setting  and  unsetting  shell
       options.

HISTORY EXPANSION
       The  shell  supports a history expansion feature that is similar to the
       history expansion in csh.  This section describes what syntax  features
       are  available.   This  feature  is  enabled by default for interactive
       shells, and can be disabled using the +H option to the set builtin com-
       mand (see SHELL BUILTIN COMMANDS below).  Non-interactive shells do not
       perform history expansion by default.

       History expansions introduce words from the history list into the input
       stream,  making  it  easy to repeat commands, insert the arguments to a
       previous command into the current input line, or fix errors in previous
       commands quickly.

       History  expansion  is  performed  immediately after a complete line is
       read, before the shell breaks it into words.  It  takes  place  in  two
       parts.   The  first is to determine which line from the history list to
       use during substitution.  The second is to select portions of that line
       for inclusion into the current one.  The line selected from the history
       is the event, and the portions of that line that  are  acted  upon  are
       words.   Various  modifiers  are  available  to manipulate the selected
       words.  The line is broken into words in the same fashion as when read-
       ing  input, so that several metacharacter-separated words surrounded by
       quotes are considered one word.  History expansions are  introduced  by
       the  appearance  of  the  history  expansion  character,  which is !! by
       default.  Only backslash (\\) and single quotes can  quote  the  history
       expansion character.

       Several  characters inhibit history expansion if found immediately fol-
       lowing the history expansion character, even if it is unquoted:  space,
       tab,  newline,  carriage return, and ==.  If the extglob shell option is
       enabled, (( will also inhibit expansion.

       Several shell options settable with the shopt builtin may  be  used  to
       tailor  the  behavior  of  history  expansion.  If the histverify shell
       option is enabled (see the description of the shopt builtin), and read-
       line is being used, history substitutions are not immediately passed to
       the shell parser.  Instead, the expanded  line  is  reloaded  into  the
       readline editing buffer for further modification.  If readline is being
       used, and the histreedit shell option is enabled, a failed history sub-
       stitution will be reloaded into the readline editing buffer for correc-
       tion.  The -p option to the history builtin command may be used to  see
       what a history expansion will do before using it.  The -s option to the
       history builtin may be used to add commands to the end of  the  history
       list  without  actually  executing them, so that they are available for
       subsequent recall.

       The shell allows control of the various characters used by the  history
       expansion mechanism (see the description of histchars above under Shell
       Variables).

   Event Designators
       An event designator is a reference to a command line entry in the  his-
       tory list.

       !!      Start  a  history substitution, except when followed by a blank,
              newline, carriage return, = or ( (when the extglob shell  option
              is enabled using the shopt builtin).
       !!_n     Refer to command line _n.
       !!--_n    Refer to the current command line minus _n.
       !!!!     Refer to the previous command.  This is a synonym for `!-1'.
       !!string
              Refer to the most recent command starting with string.
       !!??string[[??]]
              Refer  to the most recent command containing string.  The trail-
              ing ?? may be omitted if string is followed immediately by a new-
              line.
       ^^string1^^string2^^
              Quick  substitution.  Repeat the last command, replacing string1
              with string2.  Equivalent to ``!!:s/string1/string2/'' (see Mod-
              ifiers below).
       !!##     The entire command line typed so far.

   Word Designators
       Word  designators are used to select desired words from the event.  A ::
       separates the event specification from the word designator.  It may  be
       omitted  if  the word designator begins with a ^^, $$, **, --, or %%.  Words
       are numbered from the beginning of the line, with the first word  being
       denoted  by  0  (zero).  Words are inserted into the current line sepa-
       rated by single spaces.

       00 (zero)
              The zeroth word.  For the shell, this is the command word.
       _n      The _nth word.
       ^^      The first argument.  That is, word 1.
       $$      The last argument.
       %%      The word matched by the most recent `?string?' search.
       _x--_y    A range of words; `-_y' abbreviates `0-_y'.
       **      All of the words but the zeroth.  This is a synonym  for  `_1_-_$'.
              It  is  not  an  error to use ** if there is just one word in the
              event; the empty string is returned in that case.
       x*     Abbreviates _x_-_$.
       x-     Abbreviates x-$ like xx**, but omits the last word.

       If a word designator is supplied without an  event  specification,  the
       previous command is used as the event.

   Modifiers
       After  the optional word designator, there may appear a sequence of one
       or more of the following modifiers, each preceded by a `:'.

       hh      Remove a trailing file name component, leaving only the head.
       tt      Remove all leading file name components, leaving the tail.
       rr      Remove a trailing suffix of the form .xxx, leaving the basename.
       ee      Remove all but the trailing suffix.
       pp      Print the new command but do not execute it.
       qq      Quote the substituted words, escaping further substitutions.
       xx      Quote  the  substituted words as with qq, but break into words at
              blanks and newlines.
       ss//old//new//
              Substitute new for the first occurrence  of  old  in  the  event
              line.   Any  delimiter  can  be  used  in place of /.  The final
              delimiter is optional if it is the last character of  the  event
              line.   The delimiter may be quoted in old and new with a single
              backslash.  If & appears in new, it is replaced by old.  A  sin-
              gle  backslash  will  quote the &.  If old is null, it is set to
              the last old substituted, or, if no previous  history  substitu-
              tions took place, the last string in a !!??string[[??]]  search.
       &&      Repeat the previous substitution.
       gg      Cause changes to be applied over the entire event line.  This is
              used in conjunction with `::ss' (e.g.,  `:gs/old//new//')  or  `::&&'.
              If  used with `::ss', any delimiter can be used in place of /, and
              the final delimiter is optional if it is the last  character  of
              the event line.  An aa may be used as a synonym for gg.
       GG      Apply  the following `ss' modifier once to each word in the event
              line.

SHELL BUILTIN COMMANDS
       Unless otherwise noted, each builtin command documented in this section
       as accepting options preceded by -- accepts ---- to signify the end of the
       options.  For example, the ::, true, false, and  test  builtins  do  not
       accept options.
       :: [arguments]
              No  effect;  the command does nothing beyond expanding arguments
              and performing any specified redirections.  A zero exit code  is
              returned.

        ..  filename [arguments]
       source filename [arguments]
              Read  and  execute  commands  from filename in the current shell
              environment and return the exit status of the last command  exe-
              cuted from filename.  If filename does not contain a slash, file
              names in PATH are used to find the  directory  containing  file-
              name.   The  file  searched  for in PATH need not be executable.
              When bash is  not  in  posix  mode,  the  current  directory  is
              searched  if no file is found in PATH.  If the sourcepath option
              to the shopt builtin command is turned  off,  the  PATH  is  not
              searched.   If any arguments are supplied, they become the posi-
              tional parameters when  filename  is  executed.   Otherwise  the
              positional  parameters  are unchanged.  The return status is the
              status of the last command exited within the  script  (0  if  no
              commands  are  executed),  and false if filename is not found or
              cannot be read.

       alias [-p] [name[=value] ...]
              Alias with no arguments or with the -p option prints the list of
              aliases  in  the form alias name=value on standard output.  When
              arguments are supplied, an alias is defined for each name  whose
              value is given.  A trailing space in  value causes the next word
              to be checked for alias substitution when the alias is expanded.
              For  each  name  in the argument list for which no value is sup-
              plied, the name and  value  of  the  alias  is  printed.   Alias
              returns  true unless a name is given for which no alias has been
              defined.

       bg [jobspec ...]
              Resume each suspended job jobspec in the background,  as  if  it
              had been started with &&.  If jobspec is not present, the shell's
              notion of the current job is used.  bg jobspec returns 0  unless
              run  when  job control is disabled or, when run with job control
              enabled, any specified jobspec was  not  found  or  was  started
              without job control.

       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
              Display  current  readline key and function bindings, bind a key
              sequence to a readline function or  macro,  or  set  a  readline
              variable.   Each  non-option  argument  is a command as it would
              appear in .inputrc, but each binding or command must  be  passed
              as  a  separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
              Options, if supplied, have the following meanings:
              -m keymap
                     Use keymap as the keymap to be affected by the subsequent
                     bindings.  Acceptable keymap names are emacs, emacs-stan-
                     dard, emacs-meta, emacs-ctlx,  vi,  vi-move,  vi-command,
                     and  vi-insert.  vi is equivalent to vi-command; emacs is
                     equivalent to emacs-standard.
              -l     List the names of all readline functions.
              -p     Display readline function names and bindings  in  such  a
                     way that they can be re-read.
              -P     List current readline function names and bindings.
              -v     Display  readline variable names and values in such a way
                     that they can be re-read.
              -V     List current readline variable names and values.
              -s     Display readline key sequences bound to  macros  and  the
                     strings  they  output  in such a way that they can be re-
                     read.
              -S     Display readline key sequences bound to  macros  and  the
                     strings they output.
              -f filename
                     Read key bindings from filename.
              -q function
                     Query about which keys invoke the named function.
              -u function
                     Unbind all keys bound to the named function.
              -r keyseq
                     Remove any current binding for keyseq.
              -x keyseq::shell-command
                     Cause  shell-command  to  be  executed whenever keyseq is
                     entered.

              The return value is 0 unless an unrecognized option is given  or
              an error occurred.

       break [_n]
              Exit  from  within a for, while, until, or select loop.  If _n is
              specified, break _n levels.  _n must be >= 1.   If  _n  is  greater
              than  the  number  of  enclosing  loops, all enclosing loops are
              exited.  The return value is 0 unless the shell is not executing
              a loop when break is executed.

       builtin shell-builtin [arguments]
              Execute  the  specified shell builtin, passing it arguments, and
              return its exit status.  This is useful when defining a function
              whose  name  is the same as a shell builtin, retaining the func-
              tionality of the builtin within the function.  The cd builtin is
              commonly  redefined  this  way.   The  return status is false if
              shell-builtin is not a shell builtin command.

       cd [-L|-P] [dir]
              Change the current directory to dir.  The variable HOME  is  the
              default  dir.   The  variable CDPATH defines the search path for
              the directory containing dir.  Alternative  directory  names  in
              CDPATH  are  separated by a colon (:).  A null directory name in
              CDPATH is the same as the current directory,  i.e.,  ``..''.   If
              dir  begins  with  a  slash (/), then CDPATH is not used. The -P
              option says to use the physical directory structure  instead  of
              following  symbolic  links  (see  also  the -P option to the set
              builtin command); the -L option forces symbolic links to be fol-
              lowed.   An  argument  of -- is equivalent to $OLDPWD.  If a non-
              empty directory name from CDPATH is used, or if -- is  the  first
              argument,  and  the directory change is successful, the absolute
              pathname of the new working directory is written to the standard
              output.   The return value is true if the directory was success-
              fully changed; false otherwise.

       caller [expr]
              Returns the context of any active subroutine call (a shell func-
              tion  or a script executed with the .. or source builtins.  With-
              out expr, caller displays the line number and source filename of
              the  current subroutine call.  If a non-negative integer is sup-
              plied as expr, caller displays the line number, subroutine name,
              and  source  file  corresponding to that position in the current
              execution call stack.  This extra information may be  used,  for
              example,  to print a stack trace.  The current frame is frame 0.
              The return value is 0 unless the shell is not executing  a  sub-
              routine  call or expr does not correspond to a valid position in
              the call stack.

       command [-pVv] command [arg ...]
              Run command with args  suppressing  the  normal  shell  function
              lookup.  Only builtin commands or commands found in the PATH are
              executed.  If the -p option is given, the search for command  is
              performed  using  a default value for PATH that is guaranteed to
              find all of the standard utilities.  If  either  the  -V  or  -v
              option is supplied, a description of command is printed.  The -v
              option causes a single word indicating the command or file  name
              used to invoke command to be displayed; the -V option produces a
              more verbose description.  If the -V or -v option  is  supplied,
              the  exit  status  is  0 if command was found, and 1 if not.  If
              neither option is supplied and an error occurred or command can-
              not  be found, the exit status is 127.  Otherwise, the exit sta-
              tus of the command builtin is the exit status of command.

       compgen [option] [word]
              Generate possible completion matches for word according  to  the
              options,  which  may  be  any  option  accepted  by the complete
              builtin with the exception of -p and -r, and write  the  matches
              to  the  standard  output.  When using the -F or -C options, the
              various shell  variables  set  by  the  programmable  completion
              facilities, while available, will not have useful values.

              The  matches  will  be  generated in the same way as if the pro-
              grammable completion code had generated  them  directly  from  a
              completion specification with the same flags.  If word is speci-
              fied, only those completions matching word will be displayed.

              The return value is true unless an invalid option  is  supplied,
              or no matches were generated.

       complete  [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W
       wordlist] [-P prefix] [-S suffix]
              [-X filterpat] [-F function] [-C command] name [name _._._.]
       complete -pr [name ...]
              Specify  how arguments to each name should be completed.  If the
              -p option is supplied, or if no options are  supplied,  existing
              completion  specifications are printed in a way that allows them
              to be reused as input.  The -r option removes a completion spec-
              ification  for each name, or, if no names are supplied, all com-
              pletion specifications.

              The process of applying  these  completion  specifications  when
              word  completion  is  attempted  is  described  above under Pro-
              grammable Completion.

              Other options, if specified, have the following  meanings.   The
              arguments  to the -G, -W, and -X options (and, if necessary, the
              -P and -S options) should be quoted to protect them from  expan-
              sion before the complete builtin is invoked.
              -o comp-option
                      The  comp-option  controls  several aspects of the comp-
                      spec's behavior beyond the simple generation of  comple-
                      tions.  comp-option may be one of:
                      bashdefault
                              Perform the rest of the default bash completions
                              if the compspec generates no matches.
                      default Use readline's default  filename  completion  if
                              the compspec generates no matches.
                      dirnames
                              Perform  directory  name completion if the comp-
                              spec generates no matches.
                      filenames
                              Tell readline that the compspec generates  file-
                              names,  so  it can perform any filename-specific
                              processing (like adding  a  slash  to  directory
                              names or suppressing trailing spaces).  Intended
                              to be used with shell functions.
                      nospace Tell  readline  not  to  append  a  space   (the
                              default)  to  words  completed at the end of the
                              line.
                      plusdirs
                              After any matches defined by  the  compspec  are
                              generated,    directory   name   completion   is
                              attempted and  any  matches  are  added  to  the
                              results of the other actions.
              -A action
                      The  action  may  be  one of the following to generate a
                      list of possible completions:
                      alias   Alias names.  May also be specified as -a.
                      arrayvar
                              Array variable names.
                      binding Readline key binding names.
                      builtin Names of shell builtin commands.   May  also  be
                              specified as -b.
                      command Command names.  May also be specified as -c.
                      directory
                              Directory names.  May also be specified as -d.
                      disabled
                              Names of disabled shell builtins.
                      enabled Names of enabled shell builtins.
                      export  Names  of exported shell variables.  May also be
                              specified as -e.
                      file    File names.  May also be specified as -f.
                      function
                              Names of shell functions.
                      group   Group names.  May also be specified as -g.
                      helptopic
                              Help topics as accepted by the help builtin.
                      hostname
                              Hostnames, as taken from the file  specified  by
                              the HOSTFILE shell variable.
                      job     Job  names,  if job control is active.  May also
                              be specified as -j.
                      keyword Shell reserved words.  May also be specified  as
                              -k.
                      running Names of running jobs, if job control is active.
                      service Service names.  May also be specified as -s.
                      setopt  Valid arguments for the -o  option  to  the  set
                              builtin.
                      shopt   Shell  option  names  as  accepted  by the shopt
                              builtin.
                      signal  Signal names.
                      stopped Names of stopped jobs, if job control is active.
                      user    User names.  May also be specified as -u.
                      variable
                              Names of all shell variables.  May also be spec-
                              ified as -v.
              -G globpat
                      The filename expansion pattern globpat  is  expanded  to
                      generate the possible completions.
              -W wordlist
                      The  wordlist  is  split using the characters in the IFS
                      special variable as delimiters, and each resultant  word
                      is  expanded.   The possible completions are the members
                      of the resultant list which match the  word  being  com-
                      pleted.
              -C command
                      command  is  executed in a subshell environment, and its
                      output is used as the possible completions.
              -F function
                      The shell function function is executed in  the  current
                      shell  environment.  When it finishes, the possible com-
                      pletions are retrieved from the value of  the  COMPREPLY
                      array variable.
              -X filterpat
                      filterpat  is  a pattern as used for filename expansion.
                      It is applied to the list of possible completions gener-
                      ated  by  the  preceding options and arguments, and each
                      completion matching filterpat is removed from the  list.
                      A  leading  !!  in filterpat negates the pattern; in this
                      case, any completion not matching filterpat is  removed.
              -P prefix
                      prefix  is  added at the beginning of each possible com-
                      pletion after all other options have been applied.
              -S suffix
                      suffix is appended to each possible completion after all
                      other options have been applied.

              The  return  value is true unless an invalid option is supplied,
              an option other than -p or -r is supplied without a  name  argu-
              ment,  an  attempt  is made to remove a completion specification
              for a name for which no specification exists, or an error occurs
              adding a completion specification.

       continue [_n]
              Resume the next iteration of the enclosing for, while, until, or
              select loop.  If _n is specified, resume  at  the  _nth  enclosing
              loop.   _n  must  be  >=  1.   If _n is greater than the number of
              enclosing loops, the  last  enclosing  loop  (the  ``top-level''
              loop) is resumed.  The return value is 0 unless the shell is not
              executing a loop when continue is executed.

       declare [-afFirtx] [-p] [name[=value] ...]
       typeset [-afFirtx] [-p] [name[=value] ...]
              Declare variables and/or give them attributes.  If no names  are
              given  then display the values of variables.  The -p option will
              display the attributes and values of  each  name.   When  -p  is
              used,  additional  options  are ignored.  The -F option inhibits
              the display of function definitions; only the function name  and
              attributes are printed.  If the extdebug shell option is enabled
              using shopt, the source file name  and  line  number  where  the
              function  is  defined  are  displayed  as  well.   The -F option
              implies -f.  The following options can be used to restrict  out-
              put  to  variables with the specified attribute or to give vari-
              ables attributes:
              -a     Each name is an array variable (see Arrays above).
              -f     Use function names only.
              -i     The variable is treated as an integer; arithmetic evalua-
                     tion  (see  ARITHMETIC EVALUATION )) is performed when the
                     variable is assigned a value.
              -r     Make names readonly.  These names cannot then be assigned
                     values by subsequent assignment statements or unset.
              -t     Give  each  name  the  trace attribute.  Traced functions
                     inherit the DEBUG  and  RETURN  traps  from  the  calling
                     shell.   The  trace  attribute has no special meaning for
                     variables.
              -x     Mark names for export  to  subsequent  commands  via  the
                     environment.

              Using  `+'  instead of `-' turns off the attribute instead, with
              the exception that +a may not be used to destroy an array  vari-
              able.   When  used in a function, makes each name local, as with
              the local command.  If a variable name is  followed  by  =value,
              the  value of the variable is set to value.  The return value is
              0 unless an invalid option is encountered, an attempt is made to
              define  a  function  using ``-f foo=bar'', an attempt is made to
              assign a value to a readonly variable, an  attempt  is  made  to
              assign  a  value to an array variable without using the compound
              assignment syntax (see Arrays above), one of the names is not  a
              valid  shell variable name, an attempt is made to turn off read-
              only status for a readonly variable, an attempt is made to  turn
              off array status for an array variable, or an attempt is made to
              display a non-existent function with -f.

       dirs [-clpv] [[++_n]] [[--_n]]
              Without options,  displays  the  list  of  currently  remembered
              directories.   The  default  display  is  on  a single line with
              directory names separated by spaces.  Directories are  added  to
              the  list  with  the  pushd  command;  the  popd command removes
              entries from the list.
              ++_n     Displays the _nth entry counting from the left of the list
                     shown by dirs when invoked without options, starting with
                     zero.
              --_n     Displays the _nth entry counting from  the  right  of  the
                     list shown by dirs when invoked without options, starting
                     with zero.
              -c     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              -l     Produces  a  longer  listing;  the default listing format
                     uses a tilde to denote the home directory.
              -p     Print the directory stack with one entry per line.
              -v     Print the directory stack with one entry per  line,  pre-
                     fixing each entry with its index in the stack.

              The  return value is 0 unless an invalid option is supplied or _n
              indexes beyond the end of the directory stack.

       disown [-ar] [-h] [jobspec ...]
              Without options, each jobspec  is  removed  from  the  table  of
              active  jobs.   If  the  -h option is given, each jobspec is not
              removed from the table, but is marked so that SIGHUP is not sent
              to  the  job  if  the shell receives a SIGHUP.  If no jobspec is
              present, and neither the -a nor the -r option is  supplied,  the
              current  job  is used.  If no jobspec is supplied, the -a option
              means to remove or mark all jobs; the -r option without  a  job-
              spec  argument  restricts operation to running jobs.  The return
              value is 0 unless a jobspec does not specify a valid job.

       echo [-neE] [arg ...]
              Output the args, separated by spaces,  followed  by  a  newline.
              The return status is always 0.  If -n is specified, the trailing
              newline is suppressed.  If the -e option is  given,  interpreta-
              tion  of  the following backslash-escaped characters is enabled.
              The -E option disables the interpretation of these escape  char-
              acters,  even  on systems where they are interpreted by default.
              The xpg_echo shell option may be used to  dynamically  determine
              whether  or not echo expands these escape characters by default.
              echo does not interpret ---- to mean the  end  of  options.   echo
              interprets the following escape sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress trailing newline
              \e     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\\\     backslash
              \\00nnn  the  eight-bit  character  whose value is the octal value
                     nnn (zero to three octal digits)
              \\nnn   the eight-bit character whose value is  the  octal  value
                     nnn (one to three octal digits)
              \\xx_H_H   the  eight-bit  character  whose value is the hexadecimal
                     value HH (one or two hex digits)

       enable [-adnps] [-f filename] [name ...]
              Enable and disable builtin shell commands.  Disabling a  builtin
              allows a disk command which has the same name as a shell builtin
              to be executed without specifying a full pathname,  even  though
              the  shell  normally searches for builtins before disk commands.
              If -n is used, each  name  is  disabled;  otherwise,  names  are
              enabled.  For example, to use the test binary found via the PATH
              instead of the shell builtin version, run  ``enable  -n  test''.
              The  -f  option  means to load the new builtin command name from
              shared object filename, on systems that support dynamic loading.
              The  -d  option will delete a builtin previously loaded with -f.
              If no name arguments are given, or if the -p option is supplied,
              a list of shell builtins is printed.  With no other option argu-
              ments, the list consists of all enabled shell builtins.   If  -n
              is  supplied, only disabled builtins are printed.  If -a is sup-
              plied, the list printed includes all builtins, with  an  indica-
              tion  of whether or not each is enabled.  If -s is supplied, the
              output is restricted to the POSIX special builtins.  The  return
              value  is  0 unless a name is not a shell builtin or there is an
              error loading a new builtin from a shared object.

       eval [arg ...]
              The args are read and concatenated together into a  single  com-
              mand.   This command is then read and executed by the shell, and
              its exit status is returned as the value of eval.  If there  are
              no args, or only null arguments, eval returns 0.

       exec [-cl] [-a name] [command [arguments]]
              If  command is specified, it replaces the shell.  No new process
              is created.  The arguments become the arguments to command.   If
              the -l option is supplied, the shell places a dash at the begin-
              ning of the zeroth arg passed to command.  This is what login(1)
              does.  The -c option causes command to be executed with an empty
              environment.  If -a is supplied, the shell passes  name  as  the
              zeroth  argument  to the executed command.  If command cannot be
              executed for some reason, a non-interactive shell exits,  unless
              the  shell  option execfail is enabled, in which case it returns
              failure.  An interactive shell returns failure if the file  can-
              not  be executed.  If command is not specified, any redirections
              take effect in the current shell, and the return  status  is  0.
              If there is a redirection error, the return status is 1.

       exit [_n]
              Cause  the  shell  to exit with a status of _n.  If _n is omitted,
              the exit status is that of the last command executed.  A trap on
              EXIT is executed before the shell terminates.

       export [-fn] [name[=word]] ...
       export -p
              The  supplied names are marked for automatic export to the envi-
              ronment of subsequently executed commands.  If the -f option  is
              given,  the names refer to functions.  If no names are given, or
              if the -p option is supplied, a  list  of  all  names  that  are
              exported  in  this  shell  is printed.  The -n option causes the
              export property to be removed from each  name.   If  a  variable
              name  is  followed by =word, the value of the variable is set to
              word.  export returns an exit status  of  0  unless  an  invalid
              option  is  encountered,  one  of the names is not a valid shell
              variable name, or -f is supplied with a name that is not a func-
              tion.

       fc [-e ename] [-nlr] [first] [last]
       fc -s [pat=rep] [cmd]
              Fix  Command.  In the first form, a range of commands from first
              to last is selected from the history list.  First and  last  may
              be  specified  as a string (to locate the last command beginning
              with that string) or as a number  (an  index  into  the  history
              list, where a negative number is used as an offset from the cur-
              rent command number).  If last is not specified it is set to the
              current  command  for  listing (so that ``fc -l -10'' prints the
              last 10 commands) and to first otherwise.  If first is not spec-
              ified  it is set to the previous command for editing and -16 for
              listing.

              The -n option suppresses the command numbers when listing.   The
              -r  option reverses the order of the commands.  If the -l option
              is given, the commands are listed on  standard  output.   Other-
              wise,  the editor given by ename is invoked on a file containing
              those commands.  If ename is not given, the value of the  FCEDIT
              variable  is used, and the value of EDITOR if FCEDIT is not set.
              If neither variable is set, vi is used.  When  editing  is  com-
              plete, the edited commands are echoed and executed.

              In  the  second form, command is re-executed after each instance
              of pat is replaced by rep.  A useful alias to use with  this  is
              ``r="fc  -s"'',  so  that  typing ``r c' runs the last command
              beginning with `c' and typing ``r'' re-executes the last com-
              mand.

              If  the  first  form  is  used,  the return value is 0 unless an
              invalid option is encountered or first or last  specify  history
              lines  out  of  range.  If the -e option is supplied, the return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form is used, the return status is that of the  command  re-exe-
              cuted,  unless  cmd  does  not  specify a valid history line, in
              which case fc returns failure.

       fg [jobspec]
              Resume jobspec in the foreground, and make it the  current  job.
              If jobspec is not present, the shell's notion of the current job
              is used.  The return value is that of the  command  placed  into
              the  foreground,  or failure if run when job control is disabled
              or, when run with job control enabled, if jobspec does not spec-
              ify  a  valid  job  or  jobspec specifies a job that was started
              without job control.

       getopts optstring name [args]
              getopts is used by shell procedures to parse positional  parame-
              ters.   optstring  contains  the  option characters to be recog-
              nized; if a character is followed by  a  colon,  the  option  is
              expected  to have an argument, which should be separated from it
              by white space.  The colon and question mark characters may  not
              be  used as option characters.  Each time it is invoked, getopts
              places the next option in the shell variable name,  initializing
              name if it does not exist, and the index of the next argument to
              be processed into the variable OPTIND.  OPTIND is initialized to
              1  each  time  the  shell or a shell script is invoked.  When an
              option requires an argument, getopts places that  argument  into
              the  variable OPTARG.  The shell does not reset OPTIND automati-
              cally; it must be  manually  reset  between  multiple  calls  to
              getopts within the same shell invocation if a new set of parame-
              ters is to be used.

              When the end of options is encountered,  getopts  exits  with  a
              return  value  greater than zero.  OPTIND is set to the index of
              the first non-option argument, and name is set to ?.

              getopts normally parses the positional parameters, but  if  more
              arguments are given in args, getopts parses those instead.

              getopts  can  report errors in two ways.  If the first character
              of optstring is a colon, silent error  reporting  is  used.   In
              normal  operation  diagnostic  messages are printed when invalid
              options or missing option arguments  are  encountered.   If  the
              variable  OPTERR  is  set  to  0, no error messages will be dis-
              played, even if the first character of optstring is not a colon.

              If an invalid option is seen, getopts places ? into name and, if
              not silent, prints an  error  message  and  unsets  OPTARG.   If
              getopts  is  silent,  the  option  character  found is placed in
              OPTARG and no diagnostic message is printed.

              If a required argument is not found, and getopts is not  silent,
              a  question  mark  (??) is placed in name, OPTARG is unset, and a
              diagnostic message is printed.  If getopts  is  silent,  then  a
              colon  (::)  is  placed  in  name and OPTARG is set to the option
              character found.

              getopts returns true if an option, specified or unspecified,  is
              found.  It returns false if the end of options is encountered or
              an error occurs.

       hash [-lr] [-p filename] [-dt] [name]
              For each name, the full file name of the command  is  determined
              by searching the directories in $PATH and remembered.  If the -p
              option is supplied, no path search is performed, and filename is
              used as the full file name of the command.  The -r option causes
              the shell to forget all remembered  locations.   The  -d  option
              causes the shell to forget the remembered location of each name.
              If the -t option is supplied, the full pathname  to  which  each
              name  corresponds  is  printed.   If multiple name arguments are
              supplied with -t, the name is printed  before  the  hashed  full
              pathname.  The -l option causes output to be displayed in a for-
              mat that may be reused as input.  If no arguments are given,  or
              if only -l is supplied, information about remembered commands is
              printed.  The return status is true unless a name is  not  found
              or an invalid option is supplied.

       help [-s] [pattern]
              Display  helpful information about builtin commands.  If pattern
              is specified, help gives detailed help on all commands  matching
              pattern;  otherwise  help for all the builtins and shell control
              structures is printed.  The -s option restricts the  information
              displayed  to  a  short  usage synopsis.  The return status is 0
              unless no command matches pattern.

       history [[_n]]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg _._._.]
       history -s arg [arg _._._.]
              With no options, display the command history list with line num-
              bers.  Lines listed with a ** have been modified.  An argument of
              _n lists only the last _n lines.  If the shell variable  HISTTIME-
              FORMAT  is  set  and not null, it is used as a format string for
              strftime(3) to display the time stamp associated with each  dis-
              played  history  entry.  No intervening blank is printed between
              the formatted time stamp and the history line.  If  filename  is
              supplied,  it  is  used as the name of the history file; if not,
              the value of HISTFILE is used.  Options, if supplied,  have  the
              following meanings:
              -c     Clear the history list by deleting all the entries.
              -d offset
                     Delete the history entry at position offset.
              -a     Append  the  ``new'' history lines (history lines entered
                     since the beginning of the current bash session)  to  the
                     history file.
              -n     Read  the history lines not already read from the history
                     file into the current  history  list.   These  are  lines
                     appended  to  the history file since the beginning of the
                     current bash session.
              -r     Read the contents of the history file and use them as the
                     current history.
              -w     Write  the current history to the history file, overwrit-
                     ing the history file's contents.
              -p     Perform history substitution on the  following  args  and
                     display  the  result  on  the  standard output.  Does not
                     store the results in the history list.  Each arg must  be
                     quoted to disable normal history expansion.
              -s     Store  the  args  in  the history list as a single entry.
                     The last command in the history list  is  removed  before
                     the args are added.

              If the HISTTIMEFORMAT is set, the time stamp information associ-
              ated with each history entry is written  to  the  history  file.
              The  return  value is 0 unless an invalid option is encountered,
              an error occurs while reading or writing the  history  file,  an
              invalid  offset is supplied as an argument to -d, or the history
              expansion supplied as an argument to -p fails.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              -l     List process IDs in addition to the normal information.
              -p     List  only  the  process  ID  of  the job's process group
                     leader.
              -n     Display information only about  jobs  that  have  changed
                     status  since the user was last notified of their status.
              -r     Restrict output to running jobs.
              -s     Restrict output to stopped jobs.

              If jobspec is given, output is restricted to  information  about
              that  job.   The  return status is 0 unless an invalid option is
              encountered or an invalid jobspec is supplied.

              If the -x option is supplied, jobs replaces any jobspec found in
              command  or  args  with  the corresponding process group ID, and
              executes command passing it args, returning its exit status.

       kill [-s sigspec | -n signum | --sigspec] [pid | jobspec] ...
       kill -l [sigspec | exit__status]
              Send the signal named by sigspec  or  signum  to  the  processes
              named  by  pid or jobspec.  sigspec is either a case-insensitive
              signal name such as SIGKILL (with or without the SIG prefix)  or
              a  signal  number; signum is a signal number.  If sigspec is not
              present, then SIGTERM is assumed.  An argument of -l  lists  the
              signal  names.   If any arguments are supplied when -l is given,
              the names of the signals  corresponding  to  the  arguments  are
              listed, and the return status is 0.  The exit__status argument to
              -l is a number specifying either a signal  number  or  the  exit
              status  of  a process terminated by a signal.  kill returns true
              if at least one signal was successfully sent,  or  false  if  an
              error occurs or an invalid option is encountered.

       let arg [arg ...]
              Each arg is an arithmetic expression to be evaluated (see ARITH-
              METIC EVALUATION).  If the last arg evaluates to 0, let  returns
              1; 0 is returned otherwise.

       local [option] [name[=value] ...]
              For  each  argument, a local variable named name is created, and
              assigned value.  The option can be any of the  options  accepted
              by declare.  When local is used within a function, it causes the
              variable name to have a visible scope restricted to  that  func-
              tion and its children.  With no operands, local writes a list of
              local variables to the standard output.  It is an error  to  use
              local when not within a function.  The return status is 0 unless
              local is used outside a function, an invalid name  is  supplied,
              or name is a readonly variable.

       logout Exit a login shell.

       popd [-nn] [+_n] [-_n]
              Removes  entries  from  the directory stack.  With no arguments,
              removes the top directory from the stack, and performs a  cd  to
              the new top directory.  Arguments, if supplied, have the follow-
              ing meanings:
              ++_n     Removes the _nth entry counting from the left of the  list
                     shown  by  dirs, starting with zero.  For example: ``popd
                     +0'' removes the first directory, ``popd +1'' the second.
              --_n     Removes the _nth entry counting from the right of the list
                     shown by dirs, starting with zero.  For  example:  ``popd
                     -0''  removes the last directory, ``popd -1'' the next to
                     last.
              -n     Suppresses the normal change of directory  when  removing
                     directories  from  the  stack,  so that only the stack is
                     manipulated.

              If the popd command is successful, a dirs is performed as  well,
              and  the  return  status is 0.  popd returns false if an invalid
              option is encountered, the directory stack is empty, a non-exis-
              tent directory stack entry is specified, or the directory change
              fails.

       printf [-v var] format [arguments]
              Write the formatted arguments to the standard output  under  the
              control  of  the format.  The format is a character string which
              contains three types of objects:  plain  characters,  which  are
              simply  copied  to  standard output, character escape sequences,
              which are converted and copied to the standard output, and  for-
              mat  specifications,  each  of which causes printing of the next
              successive argument.  In addition to the standard printf(1) for-
              mats,  %b  causes printf to expand backslash escape sequences in
              the corresponding argument (except that  \c  terminates  output,
              backslashes in \\'', \\"", and \\?? are not removed, and octal escapes
              beginning with \\00 may contain up to four digits), and %q  causes
              printf to output the corresponding argument in a format that can
              be reused as shell input.

              The -v option causes the output to be assigned to  the  variable
              var rather than being printed to the standard output.

              The  format  is  reused as necessary to consume all of the argu-
              ments.  If the format requires more arguments than are supplied,
              the  extra  format  specifications  behave as if a zero value or
              null string, as appropriate,  had  been  supplied.   The  return
              value is zero on success, non-zero on failure.

       pushd [-n] [dir]
       pushd [-n] [+_n] [-_n]
              Adds  a  directory to the top of the directory stack, or rotates
              the stack, making the new top of the stack the  current  working
              directory.  With no arguments, exchanges the top two directories
              and returns 0, unless the directory stack is empty.   Arguments,
              if supplied, have the following meanings:
              ++_n     Rotates  the  stack  so  that the _nth directory (counting
                     from the left of the list shown by  dirs,  starting  with
                     zero) is at the top.
              --_n     Rotates  the  stack  so  that the _nth directory (counting
                     from the right of the list shown by dirs,  starting  with
                     zero) is at the top.
              -n     Suppresses  the  normal  change  of directory when adding
                     directories to the stack,  so  that  only  the  stack  is
                     manipulated.
              dir    Adds dir to the directory stack at the top, making it the
                     new current working directory.

              If the pushd command is successful, a dirs is performed as well.
              If  the first form is used, pushd returns 0 unless the cd to dir
              fails.  With the second form, pushd returns 0 unless the  direc-
              tory  stack  is empty, a non-existent directory stack element is
              specified, or the directory change to the specified new  current
              directory fails.

       pwd [-LP]
              Print  the  absolute  pathname of the current working directory.
              The pathname printed contains no symbolic links if the -P option
              is supplied or the -o physical option to the set builtin command
              is enabled.  If the -L option is used, the pathname printed  may
              contain  symbolic links.  The return status is 0 unless an error
              occurs while reading the name of the  current  directory  or  an
              invalid option is supplied.

       read [-ers] [-u fd] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d
       delim] [name ...]
              One  line  is  read  from  the  standard input, or from the file
              descriptor fd supplied as an argument to the -u option, and  the
              first word is assigned to the first name, the second word to the
              second name, and so on, with leftover words and their  interven-
              ing  separators  assigned  to the last name.  If there are fewer
              words read from the input stream than names, the remaining names
              are  assigned  empty  values.  The characters in IFS are used to
              split the line into words.  The backslash character (\\)  may  be
              used  to  remove any special meaning for the next character read
              and for line continuation.  Options, if supplied, have the  fol-
              lowing meanings:
              -a aname
                     The words are assigned to sequential indices of the array
                     variable aname, starting at 0.  aname is unset before any
                     new  values  are  assigned.   Other  name  arguments  are
                     ignored.
              -d delim
                     The first character of delim is  used  to  terminate  the
                     input line, rather than newline.
              -e     If the standard input is coming from a terminal, readline
                     (see READLINE above) is used to obtain the line.
              -n nchars
                     read returns after reading nchars characters rather  than
                     waiting for a complete line of input.
              -p prompt
                     Display prompt on standard error, without a trailing new-
                     line, before attempting to read any input.  The prompt is
                     displayed only if input is coming from a terminal.
              -r     Backslash does not act as an escape character.  The back-
                     slash is considered to be part of the line.  In  particu-
                     lar,  a  backslash-newline pair may not be used as a line
                     continuation.
              -s     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              -t timeout
                     Cause  read  to time out and return failure if a complete
                     line of input is not read within timeout  seconds.   This
                     option  has  no  effect if read is not reading input from
                     the terminal or a pipe.
              -u fd  Read input from file descriptor fd.

              If no names are supplied, the line read is assigned to the vari-
              able  REPLY.   The  return  code  is zero, unless end-of-file is
              encountered, read times out, or an invalid  file  descriptor  is
              supplied as the argument to -u.

       readonly [-apf] [name[=word] ...]
              The  given  names are marked readonly; the values of these names
              may not be changed by subsequent assignment.  If the  -f  option
              is  supplied,  the  functions  corresponding to the names are so
              marked.  The -a option restricts the variables to arrays.  If no
              name  arguments  are  given,  or if the -p option is supplied, a
              list of all readonly names is printed.   The  -p  option  causes
              output  to be displayed in a format that may be reused as input.
              If a variable name is followed by =word, the value of the  vari-
              able  is  set to word.  The return status is 0 unless an invalid
              option is encountered, one of the names is  not  a  valid  shell
              variable name, or -f is supplied with a name that is not a func-
              tion.

       return [_n]
              Causes a function to exit with the return value specified by  _n.
              If  _n  is omitted, the return status is that of the last command
              executed in the function body.  If used outside a function,  but
              during  execution  of  a  script  by the ..  (source) command, it
              causes the shell to stop executing that script and return either
              _n  or  the  exit  status of the last command executed within the
              script as the exit status of the  script.   If  used  outside  a
              function  and  not during execution of a script by .., the return
              status is false.  Any command associated with the RETURN trap is
              executed  before execution resumes after the function or script.

       set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
              Without options, the name and value of each shell  variable  are
              displayed in a format that can be reused as input for setting or
              resetting the currently-set variables.  Read-only variables can-
              not  be  reset.  In posix mode, only shell variables are listed.
              The output is sorted according  to  the  current  locale.   When
              options  are specified, they set or unset shell attributes.  Any
              arguments remaining after the options are processed are  treated
              as  values  for  the  positional parameters and are assigned, in
              order, to $$11, $$22, ......  $$_n.  Options, if specified, have the fol-
              lowing meanings:
              -a      Automatically  mark  variables  and  functions which are
                      modified or created for export  to  the  environment  of
                      subsequent commands.
              -b      Report  the status of terminated background jobs immedi-
                      ately, rather than before the next primary prompt.  This
                      is effective only when job control is enabled.
              -e      Exit  immediately if a simple command (see SHELL GRAMMAR
                      above) exits with a non-zero status.  The shell does not
                      exit  if  the  command that fails is part of the command
                      list immediately following a  while  or  until  keyword,
                      part  of the test in an if statement, part of a &&&& or ||||
                      list, or if the command's return value is being inverted
                      via  !!.   A  trap on ERR, if set, is executed before the
                      shell exits.
              -f      Disable pathname expansion.
              -h      Remember the location of commands as they are looked  up
                      for execution.  This is enabled by default.
              -k      All  arguments  in the form of assignment statements are
                      placed in the environment for a command, not just  those
                      that precede the command name.
              -m      Monitor  mode.   Job control is enabled.  This option is
                      on by default for interactive  shells  on  systems  that
                      support  it  (see  JOB  CONTROL above).  Background pro-
                      cesses run in a separate process group and a  line  con-
                      taining  their exit status is printed upon their comple-
                      tion.
              -n      Read commands but do not execute them.  This may be used
                      to  check  a  shell  script  for syntax errors.  This is
                      ignored by interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.
                      braceexpand
                              Same as -B.
                      emacs   Use an emacs-style command line  editing  inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the --noediting option.
                      errtrace
                              Same as -E.
                      functrace
                              Same as -T.
                      errexit Same as -e.
                      hashall Same as -h.
                      histexpand
                              Same as -H.
                      history Enable command history, as described above under
                              HISTORY.  This option is on by default in inter-
                              active shells.
                      ignoreeof
                              The   effect   is   as   if  the  shell  command
                              ``IGNOREEOF=10'' had been  executed  (see  Shell
                              Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.  nolog Currently ignored.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      pipefail
                              If  set,  the  return value of a pipeline is the
                              value of the last (rightmost)  command  to  exit
                              with  a non-zero status, or zero if all commands
                              in the pipeline exit successfully.  This  option
                              is disabled by default.
                      posix   Change  the  behavior  of bash where the default
                              operation differs from the POSIX 1003.2 standard
                              to match the standard (posix mode).
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line editing interface.
                      xtrace  Same as -x.
                      If -o is supplied with no option-name, the values of the
                      current options are printed.  If +o is supplied with  no
                      option-name,  a  series  of set commands to recreate the
                      current option settings is  displayed  on  the  standard
                      output.
              -p      Turn  on  privileged  mode.   In this mode, the $ENV and
                      $BASH_ENV files are not processed, shell  functions  are
                      not  inherited  from  the environment, and the SHELLOPTS
                      variable, if it appears in the environment, is  ignored.
                      If  the shell is started with the effective user (group)
                      id not equal to the real user (group)  id,  and  the  -p
                      option  is not supplied, these actions are taken and the
                      effective user id is set to the real user id.  If the -p
                      option  is supplied at startup, the effective user id is
                      not reset.  Turning this option off causes the effective
                      user  and group ids to be set to the real user and group
                      ids.
              -t      Exit after reading and executing one command.
              -u      Treat unset variables as an error when performing param-
                      eter  expansion.   If expansion is attempted on an unset
                      variable, the shell prints an error message, and, if not
                      interactive, exits with a non-zero status.
              -v      Print shell input lines as they are read.
              -x      After  expanding  each simple command, for command, case
                      command, select command, or arithmetic for command, dis-
                      play  the expanded value of PS4, followed by the command
                      and its expanded arguments or associated word list.
              -B      The shell performs brace expansion (see Brace  Expansion
                      above).  This is on by default.
              -C      If  set,  bash  does not overwrite an existing file with
                      the >>, >>&&, and <<>> redirection operators.   This  may  be
                      overridden when creating output files by using the redi-
                      rection operator >>|| instead of >>.
              -E      If set, any trap on ERR is inherited by shell functions,
                      command  substitutions,  and commands executed in a sub-
                      shell environment.  The ERR trap is normally not  inher-
                      ited in such cases.
              -H      Enable !!  style history substitution.  This option is on
                      by default when the shell is interactive.
              -P      If set, the shell does not follow  symbolic  links  when
                      executing  commands  such  as cd that change the current
                      working  directory.   It  uses  the  physical  directory
                      structure instead.  By default, bash follows the logical
                      chain of  directories  when  performing  commands  which
                      change the current directory.
              -T      If  set,  any traps on DEBUG and RETURN are inherited by
                      shell functions,  command  substitutions,  and  commands
                      executed  in  a  subshell  environment.   The  DEBUG and
                      RETURN traps are normally not inherited in such cases.
              ----      If no arguments follow this option, then the  positional
                      parameters are unset.  Otherwise, the positional parame-
                      ters are set to the args, even if  some  of  them  begin
                      with a --.
              --       Signal  the  end of options, cause all remaining args to
                      be assigned to the positional parameters.  The -x and -v
                      options are turned off.  If there are no args, the posi-
                      tional parameters remain unchanged.

              The options are off by default unless otherwise noted.  Using  +
              rather  than  -  causes  these  options  to  be turned off.  The
              options can also be specified as arguments to an  invocation  of
              the  shell.  The current set of options may be found in $$--.  The
              return status is always true unless an invalid option is encoun-
              tered.

       shift [_n]
              The  positional  parameters  from _n+1 ... are renamed to $$11 ........
              Parameters represented by the numbers  $$##  down  to  $$##-_n+1  are
              unset.   _n  must  be a non-negative number less than or equal to
              $$##.  If _n is 0, no parameters are changed.  If _n is  not  given,
              it  is assumed to be 1.  If _n is greater than $$##, the positional
              parameters are not changed.  The return status is  greater  than
              zero if _n is greater than $$## or less than zero; otherwise 0.

       shopt [-pqsu] [-o] [optname ...]
              Toggle the values of variables controlling optional shell behav-
              ior.  With no options, or with the -p option, a list of all set-
              table options is displayed, with an indication of whether or not
              each is set.  The -p option causes output to be displayed  in  a
              form  that  may be reused as input.  Other options have the fol-
              lowing meanings:
              -s     Enable (set) each optname.
              -u     Disable (unset) each optname.
              -q     Suppresses normal output (quiet mode); the return  status
                     indicates whether the optname is set or unset.  If multi-
                     ple optname arguments are given with -q, the return  sta-
                     tus  is zero if all optnames are enabled; non-zero other-
                     wise.
              -o     Restricts the values of optname to be those  defined  for
                     the -o option to the set builtin.

              If  either  -s or -u is used with no optname arguments, the dis-
              play is limited to those options which are set or unset, respec-
              tively.   Unless otherwise noted, the shopt options are disabled
              (unset) by default.

              The return status when listing options is zero if  all  optnames
              are  enabled,  non-zero  otherwise.   When  setting or unsetting
              options, the return status is zero unless an optname  is  not  a
              valid shell option.

              The list of shopt options is:

              cdable_vars
                      If  set,  an  argument to the cd builtin command that is
                      not a directory is assumed to be the name of a  variable
                      whose value is the directory to change to.
              cdspell If set, minor errors in the spelling of a directory com-
                      ponent in a cd command will be  corrected.   The  errors
                      checked for are transposed characters, a missing charac-
                      ter, and one character too many.   If  a  correction  is
                      found,  the corrected file name is printed, and the com-
                      mand proceeds.  This option is only used by  interactive
                      shells.
              checkhash
                      If set, bash checks that a command found in the hash ta-
                      ble exists before trying to execute  it.   If  a  hashed
                      command  no  longer exists, a normal path search is per-
                      formed.
              checkwinsize
                      If set, bash checks the window size after  each  command
                      and,  if necessary, updates the values of LINES and COL-
                      UMNS.
              cmdhist If set, bash attempts to save all lines of  a  multiple-
                      line  command  in  the  same history entry.  This allows
                      easy re-editing of multi-line commands.
              dotglob If set, bash includes filenames beginning with a `.'  in
                      the results of pathname expansion.
              execfail
                      If set, a non-interactive shell will not exit if it can-
                      not execute the file specified as  an  argument  to  the
                      exec  builtin  command.   An  interactive shell does not
                      exit if exec fails.
              expand_aliases
                      If set, aliases are expanded as  described  above  under
                      ALIASES.  This option is enabled by default for interac-
                      tive shells.
              extdebug
                      If set,  behavior  intended  for  use  by  debuggers  is
                      enabled:
                      11..     The -F option to the declare builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      22..     If  the  command  run by the DEBUG trap returns a
                             non-zero value, the next command is  skipped  and
                             not executed.
                      33..     If  the  command  run by the DEBUG trap returns a
                             value of 2, and the shell is executing in a  sub-
                             routine  (a shell function or a shell script exe-
                             cuted by the .. or source  builtins),  a  call  to
                             return is simulated.
                      44..     BASH_ARGC  and BASH_ARGV are updated as described
                             in their descriptions above.
                      55..     Function tracing is enabled:   command  substitu-
                             tion, shell functions, and subshells invoked with
                             (( command )) inherit the DEBUG and RETURN traps.
                      66..     Error tracing is enabled:  command  substitution,
                             shell  functions,  and  subshells  invoked with ((
                             command )) inherit the ERROR trap.
              extglob If set, the extended pattern matching features described
                      above under Pathname Expansion are enabled.
              extquote
                      If  set,  $$'string'  and  $$"string" quoting is performed
                      within  $${{parameter}}  expansions  enclosed   in   double
                      quotes.  This option is enabled by default.
              failglob
                      If  set,  patterns  which fail to match filenames during
                      pathname expansion result in an expansion error.
              force_fignore
                      If set, the suffixes  specified  by  the  FIGNORE  shell
                      variable  cause words to be ignored when performing word
                      completion even if the ignored words are the only possi-
                      ble  completions.   See  SHELL  VARIABLES  above  for  a
                      description of  FIGNORE.   This  option  is  enabled  by
                      default.
              gnu_errfmt
                      If set, shell error messages are written in the standard
                      GNU error message format.
              histappend
                      If set, the history list is appended to the  file  named
                      by  the  value  of  the HISTFILE variable when the shell
                      exits, rather than overwriting the file.
              histreedit
                      If set, and readline is being used, a user is given  the
                      opportunity to re-edit a failed history substitution.
              histverify
                      If  set, and readline is being used, the results of his-
                      tory substitution are  not  immediately  passed  to  the
                      shell  parser.   Instead,  the  resulting line is loaded
                      into the readline editing buffer, allowing further modi-
                      fication.
              hostcomplete
                      If set, and readline is being used, bash will attempt to
                      perform hostname completion when a word containing  a  @@
                      is   being  completed  (see  Completing  under  READLINE
                      above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an inter-
                      active login shell exits.
              interactive_comments
                      If set, allow a word beginning with ## to cause that word
                      and all remaining characters on that line to be  ignored
                      in  an  interactive  shell  (see  COMMENTS above).  This
                      option is enabled by default.
              lithist If set, and the cmdhist option  is  enabled,  multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.
              login_shell
                      The shell sets this option if it is started as  a  login
                      shell  (see  INVOCATION  above).   The  value may not be
                      changed.
              mailwarn
                      If set, and a file that bash is checking  for  mail  has
                      been  accessed  since  the last time it was checked, the
                      message ``The mail in mailfile has been read''  is  dis-
                      played.
              no_empty_cmd_completion
                      If  set,  and  readline  is  being  used,  bash will not
                      attempt to search the PATH for possible completions when
                      completion is attempted on an empty line.
              nocaseglob
                      If  set,  bash  matches  filenames in a case-insensitive
                      fashion when performing pathname expansion (see Pathname
                      Expansion above).
              nocasematch
                      If  set,  bash  matches  patterns  in a case-insensitive
                      fashion when performing matching while executing case or
                      [[[[ conditional commands.
              nullglob
                      If  set,  bash allows patterns which match no files (see
                      Pathname Expansion above) to expand to  a  null  string,
                      rather than themselves.
              progcomp
                      If set, the programmable completion facilities (see Pro-
                      grammable Completion above) are enabled.  This option is
                      enabled by default.
              promptvars
                      If set, prompt strings undergo parameter expansion, com-
                      mand  substitution,  arithmetic  expansion,  and   quote
                      removal  after  being expanded as described in PROMPTING
                      above.  This option is enabled by default.
              restricted_shell
                      The  shell  sets  this  option  if  it  is  started   in
                      restricted mode (see RESTRICTED SHELL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed, allowing the startup files to dis-
                      cover whether or not a shell is restricted.
              shift_verbose
                      If set, the shift builtin prints an error  message  when
                      the shift count exceeds the number of positional parame-
                      ters.
              sourcepath
                      If set, the source (..) builtin uses the value of PATH to
                      find  the  directory  containing the file supplied as an
                      argument.  This option is enabled by default.
              xpg_echo
                      If  set,  the  echo  builtin  expands   backslash-escape
                      sequences by default.
       suspend [-f]
              Suspend  the execution of this shell until it receives a SIGCONT
              signal.  The -f option says not to complain if this is  a  login
              shell;  just  suspend anyway.  The return status is 0 unless the
              shell is a login shell and -f is not supplied, or if job control
              is not enabled.
       test expr
       [[ expr ]]
              Return  a  status  of  0 or 1 depending on the evaluation of the
              conditional expression expr.  Each operator and operand must  be
              a  separate argument.  Expressions are composed of the primaries
              described above under CONDITIONAL EXPRESSIONS.   test  does  not
              accept any options, nor does it accept and ignore an argument of
              ---- as signifying the end of options.

              Expressions may  be  combined  using  the  following  operators,
              listed in decreasing order of precedence.
              !! expr True if expr is false.
              (( expr ))
                     Returns  the value of expr.  This may be used to override
                     the normal precedence of operators.
              expr1 -aa expr2
                     True if both expr1 and expr2 are true.
              expr1 -oo expr2
                     True if either expr1 or expr2 is true.

              test and [[ evaluate conditional expressions using a set of rules
              based on the number of arguments.

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not
                     null.
              2 arguments
                     If the first argument is !!, the expression is true if and
                     only  if the second argument is null.  If the first argu-
                     ment is one of the  unary  conditional  operators  listed
                     above  under  CONDITIONAL  EXPRESSIONS, the expression is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     If the second argument is one of the  binary  conditional
                     operators listed above under CONDITIONAL EXPRESSIONS, the
                     result of the expression is the result of the binary test
                     using  the first and third arguments as operands.  If the
                     first argument is !!, the value is  the  negation  of  the
                     two-argument  test  using the second and third arguments.
                     If the first argument is exactly (( and the third argument
                     is  exactly )), the result is the one-argument test of the
                     second argument.  Otherwise,  the  expression  is  false.
                     The  -a  and -o operators are considered binary operators
                     in this case.
              4 arguments
                     If the first argument is !!, the result is the negation of
                     the  three-argument  expression composed of the remaining
                     arguments.  Otherwise, the expression is parsed and eval-
                     uated  according  to  precedence  using  the rules listed
                     above.
              5 or more arguments
                     The expression  is  parsed  and  evaluated  according  to
                     precedence using the rules listed above.

       times  Print  the  accumulated  user and system times for the shell and
              for processes run from the shell.  The return status is 0.

       trap [-lp] [[arg] sigspec ...]
              The command arg is to  be  read  and  executed  when  the  shell
              receives  signal(s)  sigspec.   If arg is absent (and there is a
              single sigspec) or --, each specified  signal  is  reset  to  its
              original  disposition  (the  value  it  had upon entrance to the
              shell).  If arg is the null string the signal specified by  each
              sigspec  is ignored by the shell and by the commands it invokes.
              If arg is not present and -p has been supplied,  then  the  trap
              commands  associated  with  each  sigspec  are displayed.  If no
              arguments are supplied or if only -p is given, trap  prints  the
              list  of  commands  associated  with each signal.  The -l option
              causes the shell to print a list of signal names and their  cor-
              responding  numbers.   Each  sigspec  is  either  a  signal name
              defined in <signal.h>, or a signal  number.   Signal  names  are
              case  insensitive  and the SIG prefix is optional.  If a sigspec
              is EXIT (0) the command arg is executed on exit from the  shell.
              If  a sigspec is DEBUG, the command arg is executed before every
              simple command, for command, case command, select command, every
              arithmetic for command, and before the first command executes in
              a shell function  (see  SHELL  GRAMMAR  above).   Refer  to  the
              description  of  the  extdebug  option  to the shopt builtin for
              details of its effect on the DEBUG trap.  If a sigspec  is  ERR,
              the  command  arg  is  executed  whenever a simple command has a
              non-zero exit status, subject to the following conditions.   The
              ERR  trap  is  not executed if the failed command is part of the
              command list immediately following a  while  or  until  keyword,
              part of the test in an if statement, part of a &&&& or |||| list, or
              if the command's return value is being inverted  via  !!.   These
              are  the  same  conditions  obeyed  by the errexit option.  If a
              sigspec is RETURN, the command arg is executed each time a shell
              function or a script executed with the .. or source builtins fin-
              ishes executing.  Signals ignored upon entry to the shell cannot
              be  trapped or reset.  Trapped signals are reset to their origi-
              nal values in a child process when it is  created.   The  return
              status  is  false  if  any  sigspec  is  invalid; otherwise trap
              returns true.

       type [-aftpP] name [name ...]
              With no options, indicate how each name would be interpreted  if
              used as a command name.  If the -t option is used, type prints a
              string which is one of alias,  keyword,  function,  builtin,  or
              file  if  name  is  an  alias,  shell  reserved  word, function,
              builtin, or disk file, respectively.  If the name is not  found,
              then  nothing  is  printed,  and  an  exit  status  of  false is
              returned.  If the -p option is used,  type  either  returns  the
              name of the disk file that would be executed if name were speci-
              fied as a command name, or nothing if ``type -t name'' would not
              return  file.  The -P option forces a PATH search for each name,
              even if ``type -t name'' would not return file.  If a command is
              hashed,  -p  and  -P print the hashed value, not necessarily the
              file that appears first in PATH.  If the -a option is used, type
              prints  all of the places that contain an executable named name.
              This includes aliases and functions,  if  and  only  if  the  -p
              option  is  not  also used.  The table of hashed commands is not
              consulted when using -a.  The -f option suppresses  shell  func-
              tion  lookup, as with the command builtin.  type returns true if
              any of the arguments are found, false if none are found.

       ulimit [-SHacdflmnpstuv [limit]]
              Provides control over the resources available to the  shell  and
              to  processes started by it, on systems that allow such control.
              The -H and -S options specify that the hard or soft limit is set
              for  the  given resource.  A hard limit cannot be increased once
              it is set; a soft limit may be increased up to the value of  the
              hard  limit.   If  neither -H nor -S is specified, both the soft
              and hard limits are set.  The value of limit can be a number  in
              the unit specified for the resource or one of the special values
              hard, soft, or unlimited,  which  stand  for  the  current  hard
              limit,  the  current soft limit, and no limit, respectively.  If
              limit is omitted, the current value of the  soft  limit  of  the
              resource  is  printed, unless the -H option is given.  When more
              than one resource is specified, the  limit  name  and  unit  are
              printed before the value.  Other options are interpreted as fol-
              lows:
              -a     All current limits are reported
              -c     The maximum size of core files created
              -d     The maximum size of a process's data segment
              -f     The maximum size of files created by the shell
              -l     The maximum size that may be locked into memory
              -m     The maximum resident set size
              -n     The maximum number of open file descriptors (most systems
                     do not allow this value to be set)
              -p     The pipe size in 512-byte blocks (this may not be set)
              -s     The maximum stack size
              -t     The maximum amount of cpu time in seconds
              -u     The  maximum  number  of  processes available to a single
                     user
              -v     The maximum amount of virtual  memory  available  to  the
                     shell

              If limit is given, it is the new value of the specified resource
              (the -a option is display only).  If no option is given, then -f
              is  assumed.  Values are in 1024-byte increments, except for -t,
              which is in seconds, -p, which is in units of  512-byte  blocks,
              and  -n and -u, which are unscaled values.  The return status is
              0 unless an invalid option or argument is supplied, or an  error
              occurs while setting a new limit.

       umask [-p] [-S] [mode]
              The user file-creation mask is set to mode.  If mode begins with
              a digit, it is interpreted as an octal number; otherwise  it  is
              interpreted  as a symbolic mode mask similar to that accepted by
              chmod(1).  If mode is omitted, the current value of the mask  is
              printed.   The  -S  option causes the mask to be printed in sym-
              bolic form; the default output is an octal number.   If  the  -p
              option is supplied, and mode is omitted, the output is in a form
              that may be reused as input.  The return status is 0 if the mode
              was  successfully  changed  or if no mode argument was supplied,
              and false otherwise.

       unalias [-aa] [name ...]
              Remove each name from the list of defined  aliases.   If  -a  is
              supplied,  all  alias definitions are removed.  The return value
              is true unless a supplied name is not a defined alias.

       unset [-fv] [name ...]
              For each name, remove the corresponding  variable  or  function.
              If no options are supplied, or the -v option is given, each name
              refers to a shell variable.   Read-only  variables  may  not  be
              unset.   If  -f  is specified, each name refers to a shell func-
              tion, and the function definition is removed.  Each unset  vari-
              able  or function is removed from the environment passed to sub-
              sequent commands.  If any of RANDOM, SECONDS,  LINENO,  HISTCMD,
              FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special
              properties, even if they are subsequently reset.  The exit  sta-
              tus is true unless a name is readonly.

       wait [_n _._._.]
              Wait  for each specified process and return its termination sta-
              tus.  Each _n may be a process ID or a job  specification;  if  a
              job  spec  is  given,  all  processes in that job's pipeline are
              waited for.  If _n is not given, all currently active child  pro-
              cesses  are  waited  for,  and  the return status is zero.  If _n
              specifies a non-existent process or job, the  return  status  is
              127.   Otherwise,  the  return  status is the exit status of the
              last process or job waited for.

RESTRICTED SHELL
       If bash is started with the name rbash, or the -r option is supplied at
       invocation,  the  shell becomes restricted.  A restricted shell is used
       to set up an environment more controlled than the standard  shell.   It
       behaves  identically  to bash with the exception that the following are
       disallowed or not performed:

       +o      changing directories with cd

       +o      setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV

       +o      specifying command names containing //

       +o      specifying  a  file  name containing a // as an argument to the ..
              builtin command

       +o      Specifying a filename containing a slash as an argument  to  the
              -p option to the hash builtin command

       +o      importing  function  definitions  from  the shell environment at
              startup

       +o      parsing the value of SHELLOPTS from  the  shell  environment  at
              startup

       +o      redirecting output using the >, >|, <>, >&, &>, and >> redirect-
              ion operators

       +o      using the exec builtin command to replace the shell with another
              command

       +o      adding  or  deleting builtin commands with the -f and -d options
              to the enable builtin command

       +o      Using the  enable  builtin  command  to  enable  disabled  shell
              builtins

       +o      specifying the -p option to the command builtin command

       +o      turning off restricted mode with set +r or set +o restricted.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed (see COM-
       MAND EXECUTION above), rbash turns off any restrictions  in  the  shell
       spawned to execute the script.

SEE ALSO
       Bash Reference Manual, Brian Fox and Chet Ramey
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       Portable  Operating  System  Interface (POSIX) Part 2: Shell and Utili-
       ties, IEEE
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES
       /bin/bash
              The bash executable
       /etc/profile
              The systemwide initialization file, executed for login shells
       ~/.bash__profile
              The personal initialization file, executed for login shells
       ~/.bashrc
              The individual per-interactive-shell startup file
       ~/.bash__logout
              The  individual  login shell cleanup file, executed when a login
              shell exits
       ~/.inputrc
              Individual readline initialization file

AUTHORS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet@po.cwru.edu

BUG REPORTS
       If you find a bug in bash, you should report it.  But first, you should
       make  sure  that  it really is a bug, and that it appears in the latest
       version  of  bash.   The  latest  version  is  always  available   from
       ftp://ftp.gnu.org/pub/bash/.

       Once  you  have  determined that a bug actually exists, use the bashbug
       command to submit a bug report.  If you have a fix, you are  encouraged
       to  mail that as well!  Suggestions and `philosophical' bug reports may
       be mailed  to  bug-bash@gnu.org  or  posted  to  the  Usenet  newsgroup
       gnu.bash.bug.

       ALL bug reports should include:

       The version number of bash
       The hardware and operating system
       The compiler used to compile
       A description of the bug behaviour
       A short script or `recipe' which exercises the bug

       bashbug  inserts  the first three items automatically into the template
       it provides for filing a bug report.

       Comments and bug reports concerning this manual page should be directed
       to chet@po.cwru.edu.

BUGS
       It's too big and too slow.

       There are some subtle differences between bash and traditional versions
       of sh, mostly because of the POSIX specification.

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

       Compound commands and command sequences of the form `a ; b ; c' are not
       handled  gracefully  when  process  suspension  is  attempted.   When a
       process is stopped, the shell immediately executes the next command  in
       the  sequence.   It  suffices to place the sequence of commands between
       parentheses to force it into a subshell, which  may  be  stopped  as  a
       unit.

       Commands  inside  of  $$((...))  command substitution are not parsed until
       substitution is attempted.  This will delay error reporting until  some
       time after the command is entered.  For example, unmatched parentheses,
       even inside shell comments, will result in  error  messages  while  the
       construct is being read.

       Array variables may not (yet) be exported.



GNU Bash-3.1-beta1                2005 Aug 27                          BASH(1)
